Human Biology
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
Sensory Receptors and Sensations
Each type of sensory receptor detects a specific type of stimulus. Sensation occurs when nerve
impulses reach the cerebral cortex. Perception is an interpretation of the meaning of sensations.
Proprioceptors and Cutaneous Receptors
Proprioception is illustrated by the action of muscle spindles that are influenced when muscle
fibers stretch. The skin contains sensory receptors, called cutaneous receptors, for touch,
pressure, pain, and temperature.
Chemical Senses
Taste and smell are due to chemoreceptors stimulated by molecules in the environment. Taste
buds contain taste cells that communicate with sensory nerve fibers, while the chemoreceptors
for smell are neurons.
Sense of Vision
Vision is dependent on the eye, the optic nerves, and the visual areas of the cerebral cortex.
The eye has three layers: the outer layer (sclera and cornea), the middle pigmented layer
(choroid), and the inner layer (retina).
Sense of Hearing
Hearing is dependent on the ear, the cochlear nerve, and the auditory areas of the cerebral
cortex. The ear is divided into three parts: outer, middle, and inner.
Sense of Equilibrium
The ear also contains mechanoreceptors for our sense of equilibrium. Rotational equilibrium
depends on the stimulation of hair cells in the ampullae of the semicircular canals. Gravitational
equilibrium is based on the stimulation of hair cells in the utricle and the saccule.
Endocrine Glands
Endocrine glands secrete hormones into the bloodstream, and from there they are distributed
to target organs or tissues.
Hypothalamus and Pituitary Gland
Neurosecretory cells in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin,
which are stored in axon endings in the posterior pituitary until they are released.
Thyroid and Parathyroid Glands
The thyroid gland requires iodine to produce thyroxine and triiodothyronine, which increase
the metabolic rate. The parathyroid glands secrete parathyroid hormone, which raises the blood
calcium and decreases the blood phosphate levels.
Adrenal Glands
The adrenal glands respond to stress by secreting epinephrine and norepinephrine from the
adrenal medulla, and cortisol and aldosterone from the adrenal cortex.
Pancreas
The pancreatic islets secrete insulin, which lowers the blood glucose level, and glucagon,
which has the opposite effect.
Other Endocrine Glands
The gonads produce the sex hormones; the pineal gland produces melatonin, which is involved
in circadian rhythms and the development of reproductive organs; and the thymus secretes
thymosins, which stimulate T lymphocyte production and maturation.
Chemical Signals
Hormones are either steroids or peptides. Steroid hormones combine with a receptor in the
cell, and the complex attaches to and activates DNA. Reception of a peptide hormone at the
plasma membrane activates an enzyme cascade.
Male Reproductive System
In males, spermatogenesis occurs in the seminiferous tubules of the testes. The external
genitals of men are the penis and the scrotum.
Female Reproductive System
In females, oogenesis occurring in the ovaries produces one mature follicle every month. The
external genital region includes the vaginal opening, the clitoris, the labia minora, and the labia
majora.
Female Hormone Levels
In the nonpregnant female, the ovarian and uterine cycles are under hormonal control of the
hypothalamus, anterior pituitary, and female sex hormones estrogen and progesterone.
Control of Reproduction
Various birth control methods and devices are available for individuals who wish to prevent
pregnancy. Some couples may employ assisted reproductive technologies to have a child.
