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9780323871730_Chapter_010.mp3

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Chapter_010.rtf

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Audio Chapter Summaries

Patton: Structure & Function of the Body, 17th Edition

Chapter 10: Senses

Audio Chapter Summaries

Welcome to the audio review for Chapter 10: Senses.

Senses are classified as general or special.

General senses are detected by sensory organs that exist as individual cells or receptor units and are widely distributed throughout the body.

Special senses are detected by large and complex organs, or localized grouping of sensory receptors.

All sense organs have common functional characteristics:

All are able to detect a particular stimulus.

A stimulus results in generation of a nerve impulse.

A nerve impulse is processed and perceived as a sensation in the central nervous system.

Sensory receptor types are classified by the presence of a capsule and by the type of stimuli needed to activate the receptors.

Sensory receptors may be encapsulated or unencapsulated. Unencapsulated receptors are also called “free” neuron endings or “naked.”

If light is the stimulus for a receptor, it is a photoreceptor.

Chemoreceptors are stimulated by chemicals.

Pain receptors are stimulated by injury.

Changes in temperature stimulate thermoreceptors.

Movements or shape changes stimulate mechanoreceptors.

The distribution of general senses is widespread, including in deep organs of the body; single-cell receptors are common. The difference in what kind of stimuli is detected is called the mode of the sensation.

Examples of general sensory receptors and their modes include:

Free nerve endings that detect pain, temperature, and crude touch;

Tactile corpuscles (also known as Meissner corpuscles) that detect fine touch and vibration;

Bulbous corpuscles (also called Ruffini corpuscles) that detect touch and pressure;

Lamellar corpuscles (also known as Pacini corpuscles) that detect pressure and vibration;

Bulboid corpuscles (also called Krause end bulbs) that detect touch; and

Tendon organs (also called Golgi tendon organs) and muscle spindles that register proprioception.

Next, we’ll review the special senses: vision, hearing and equilibrium, taste, and smell.

The eye is the organ of vision. Its complex structure can be best understood by dividing it into three layers: the fibrous, vascular, and inner layers.

The fibrous layer is a tough outer coat that includes the sclera or “white” of the eye, and the cornea, the transparent part over the iris.

A mucous membrane known as the conjunctiva lines the eyelids and covers the fibrous layer in front. The conjunctiva is kept moist by tears secreted by the lacrimal gland.

The vascular layer has a dense network of blood vessels.

It includes the choroid, the pigmented, melanin-rich layer that prevents scattering of light and the iris, the colored part of the eye. The pupil is the hole in the center of the iris; contraction of smooth muscle dilates or constricts the pupil.

The vascular layer includes the lens as well, the transparent body behind the pupil that focuses or refracts light rays on the retina.

Near the front of the vascular layer is the ciliary muscle—just outside the edge of the iris; its contraction affects the shape of the transparent lens just behind the iris, thus altering focus for near objects.

The retina makes up most of the inner layer of the eyeball.

It contains microscopic photoreceptor cells to detect light.

Most of these receptor cells are called rods and cones because of their shapes. Rods are the receptors for night and peripheral vision and cones are the receptors for daytime and color vision.

Ganglion cells are the receptors for changing light patterns of days, months, and seasons.

Eye fluids include the aqueous humor, located in the anterior chamber in front of the lens; and the vitreous humor in the posterior chamber behind the lens.

Be sure to review the visual pathway as well as the structures of vision.

Vision detects the intensity or brightness and wavelength or color of light, as well as images and motion. Light must be focused by the eye to form a detectable image.

Impulses travel from the rods and cones in the innermost layer of the retina through the bipolar and ganglionic layers of the retina.

Nerve impulse leaves the eye through the optic nerve; the point of exit is free of receptors and is therefore called a blind spot known as the optic disk .

Visual interpretation occurs in the visual cortex of the cerebrum.

Next, we will review the special senses of hearing and equilibrium.

The ear functions in hearing and equilibrium using receptors called mechanoreceptors.

First be sure you understand the ear’s anatomy. It is divided into the external, middle, and inner ear.

The external ear includes the auricle or pinna, and the external acoustic canal. This curving canal is 2.5 centimeters (or about 1 inch) in length and ends at the tympanic membrane. It contains ceruminous glands.

The middle ear houses the ear ossicles: the malleus, incus, and stapes; and it ends in the oval window. Inflammation of the middle ear is called otitis media.

The auditory tube (also called the eustachian tube) connects the middle ear to the throat.

The inner ear consists of an odd-shaped bony space called the bony labyrinth. Filled with a watery fluid called perilymph, the bony labyrinth is divided into the vestibule, semicircular canals, and the cochlea. The vestibule is adjacent to the oval window between the semicircular canals and the cochlea.

The membranous labyrinth is a balloonlike membranous sac suspended in the perilymph; it follows the shape of the bony labyrinth and is filled with endolymph.

Now we’ll review the functions of hearing and equilibrium.

Hearing detects changes in intensity and frequency of sound waves, which are pressure waves. Sound waves, funneled by the auricle into the external acoustic canal, vibrate the tympanic membrane. Vibrations of the tympanic membrane are amplified by auditory ossicles and transmitted to the oval window. Vibrations of the oval window trigger vibrations of perilymph, which in turn vibrates the endolymph. Sensory hair cells on the spiral organ (organ of Corti) generate nerve impulses when bent by the movement of surrounding endolymph set in motion by sound waves; they can become damaged by chronic exposure to loud noise.

Equilibrium describes two types of balance: static and dynamic.

Static equilibrium is the sense of gravity.

It is detected by ciliated hair cells (mechanoreceptors) of the two maculae in the vestibule. When the head tilts, gravity pulls the heavy gel of each macula, bending the sensory cilia and producing a nerve signal.

Dynamic equilibrium is the sense of speed and direction of movement.

It is detected by ciliated hair cells (mechanoreceptors) of the crista ampullaris in the ampulla of each semicircular canal.

When speed or direction of movement of the head changes, the flow of endolymph in the semicircular canals is altered, which causes changes in the bending of sensory cilia, producing a nerve signal.

The vestibular nerve carries nerve impulses from the equilibrium receptors of the vestibule and joins with the cochlear nerve to form the vestibulocochlear nerve, also known as cranial nerve VIII.

Next, we’ll review the sense of taste, which is also called gustation.

Receptors for taste are chemoreceptors called gustatory cells, located in taste buds.

Cranial nerves VII and IX carry gustatory impulses.

Primary taste modes include

Sweet, which detects sugars;

Sour, which detects acids;

Bitter, which detects alkaline solutions;

Salty, which detects sodium ions;

Umami or savory, which detects glutamate (an amino acid).

Currently, other sensations are being studied, including metallic (to detect metal ions from some foods and blood, kokumi (to detect glutamyl peptides from fermentation or curing) and chalky (to detect calcium salts in spinach, cheeses, and wines.

Smell is the last special sense to review.

Olfactory receptors are sensory fibers of the olfactory nerve, cranial nerve I. They lie in the olfactory mucosa of the nasal cavity.

These receptors are extremely sensitive, but easily adapt and become fatigued.

Odor-causing chemicals initiate a nerve signal that is interpreted as a specific odor by the brain. Note that olfaction has a strong relationship with emotions and memory.

It is important to realize that all senses are processed and finally perceived in the brain, not in the receptors.

Sensory information is combined to form an overall sensory perception of our world.

For example, flavor is a combination of gustatory and olfactory senses; it can even be affected by other senses, such as touch, pain, and temperature. Nasal congestion interferes with stimulation of olfactory receptors and thereby dulls flavor sensations.

Another example relates to posture and balance: the senses of equilibrium with vision and proprioception combine to help us maintain a safe body position.

Note that some sensory information is processed subconsciously, and like many other functions, our senses may decline as we age.

This concludes the audio review of chapter 10.

9780323871730_Chapter_010.mp3

Blues

645.624

Chapter_010.rtf

10-4

Audio Chapter Summaries

Patton: Structure & Function of the Body, 17th Edition

Chapter 10: Senses

Audio Chapter Summaries

Welcome to the audio review for Chapter 10: Senses.

Senses are classified as general or special.

General senses are detected by sensory organs that exist as individual cells or receptor units and are widely distributed throughout the body.

Special senses are detected by large and complex organs, or localized grouping of sensory receptors.

All sense organs have common functional characteristics:

All are able to detect a particular stimulus.

A stimulus results in generation of a nerve impulse.

A nerve impulse is processed and perceived as a sensation in the central nervous system.

Sensory receptor types are classified by the presence of a capsule and by the type of stimuli needed to activate the receptors.

Sensory receptors may be encapsulated or unencapsulated. Unencapsulated receptors are also called “free” neuron endings or “naked.”

If light is the stimulus for a receptor, it is a photoreceptor.

Chemoreceptors are stimulated by chemicals.

Pain receptors are stimulated by injury.

Changes in temperature stimulate thermoreceptors.

Movements or shape changes stimulate mechanoreceptors.

The distribution of general senses is widespread, including in deep organs of the body; single-cell receptors are common. The difference in what kind of stimuli is detected is called the mode of the sensation.

Examples of general sensory receptors and their modes include:

Free nerve endings that detect pain, temperature, and crude touch;

Tactile corpuscles (also known as Meissner corpuscles) that detect fine touch and vibration;

Bulbous corpuscles (also called Ruffini corpuscles) that detect touch and pressure;

Lamellar corpuscles (also known as Pacini corpuscles) that detect pressure and vibration;

Bulboid corpuscles (also called Krause end bulbs) that detect touch; and

Tendon organs (also called Golgi tendon organs) and muscle spindles that register proprioception.

Next, we’ll review the special senses: vision, hearing and equilibrium, taste, and smell.

The eye is the organ of vision. Its complex structure can be best understood by dividing it into three layers: the fibrous, vascular, and inner layers.

The fibrous layer is a tough outer coat that includes the sclera or “white” of the eye, and the cornea, the transparent part over the iris.

A mucous membrane known as the conjunctiva lines the eyelids and covers the fibrous layer in front. The conjunctiva is kept moist by tears secreted by the lacrimal gland.

The vascular layer has a dense network of blood vessels.

It includes the choroid, the pigmented, melanin-rich layer that prevents scattering of light and the iris, the colored part of the eye. The pupil is the hole in the center of the iris; contraction of smooth muscle dilates or constricts the pupil.

The vascular layer includes the lens as well, the transparent body behind the pupil that focuses or refracts light rays on the retina.

Near the front of the vascular layer is the ciliary muscle—just outside the edge of the iris; its contraction affects the shape of the transparent lens just behind the iris, thus altering focus for near objects.

The retina makes up most of the inner layer of the eyeball.

It contains microscopic photoreceptor cells to detect light.

Most of these receptor cells are called rods and cones because of their shapes. Rods are the receptors for night and peripheral vision and cones are the receptors for daytime and color vision.

Ganglion cells are the receptors for changing light patterns of days, months, and seasons.

Eye fluids include the aqueous humor, located in the anterior chamber in front of the lens; and the vitreous humor in the posterior chamber behind the lens.

Be sure to review the visual pathway as well as the structures of vision.

Vision detects the intensity or brightness and wavelength or color of light, as well as images and motion. Light must be focused by the eye to form a detectable image.

Impulses travel from the rods and cones in the innermost layer of the retina through the bipolar and ganglionic layers of the retina.

Nerve impulse leaves the eye through the optic nerve; the point of exit is free of receptors and is therefore called a blind spot known as the optic disk .

Visual interpretation occurs in the visual cortex of the cerebrum.

Next, we will review the special senses of hearing and equilibrium.

The ear functions in hearing and equilibrium using receptors called mechanoreceptors.

First be sure you understand the ear’s anatomy. It is divided into the external, middle, and inner ear.

The external ear includes the auricle or pinna, and the external acoustic canal. This curving canal is 2.5 centimeters (or about 1 inch) in length and ends at the tympanic membrane. It contains ceruminous glands.

The middle ear houses the ear ossicles: the malleus, incus, and stapes; and it ends in the oval window. Inflammation of the middle ear is called otitis media.

The auditory tube (also called the eustachian tube) connects the middle ear to the throat.

The inner ear consists of an odd-shaped bony space called the bony labyrinth. Filled with a watery fluid called perilymph, the bony labyrinth is divided into the vestibule, semicircular canals, and the cochlea. The vestibule is adjacent to the oval window between the semicircular canals and the cochlea.

The membranous labyrinth is a balloonlike membranous sac suspended in the perilymph; it follows the shape of the bony labyrinth and is filled with endolymph.

Now we’ll review the functions of hearing and equilibrium.

Hearing detects changes in intensity and frequency of sound waves, which are pressure waves. Sound waves, funneled by the auricle into the external acoustic canal, vibrate the tympanic membrane. Vibrations of the tympanic membrane are amplified by auditory ossicles and transmitted to the oval window. Vibrations of the oval window trigger vibrations of perilymph, which in turn vibrates the endolymph. Sensory hair cells on the spiral organ (organ of Corti) generate nerve impulses when bent by the movement of surrounding endolymph set in motion by sound waves; they can become damaged by chronic exposure to loud noise.

Equilibrium describes two types of balance: static and dynamic.

Static equilibrium is the sense of gravity.

It is detected by ciliated hair cells (mechanoreceptors) of the two maculae in the vestibule. When the head tilts, gravity pulls the heavy gel of each macula, bending the sensory cilia and producing a nerve signal.

Dynamic equilibrium is the sense of speed and direction of movement.

It is detected by ciliated hair cells (mechanoreceptors) of the crista ampullaris in the ampulla of each semicircular canal.

When speed or direction of movement of the head changes, the flow of endolymph in the semicircular canals is altered, which causes changes in the bending of sensory cilia, producing a nerve signal.

The vestibular nerve carries nerve impulses from the equilibrium receptors of the vestibule and joins with the cochlear nerve to form the vestibulocochlear nerve, also known as cranial nerve VIII.

Next, we’ll review the sense of taste, which is also called gustation.

Receptors for taste are chemoreceptors called gustatory cells, located in taste buds.

Cranial nerves VII and IX carry gustatory impulses.

Primary taste modes include

Sweet, which detects sugars;

Sour, which detects acids;

Bitter, which detects alkaline solutions;

Salty, which detects sodium ions;

Umami or savory, which detects glutamate (an amino acid).

Currently, other sensations are being studied, including metallic (to detect metal ions from some foods and blood, kokumi (to detect glutamyl peptides from fermentation or curing) and chalky (to detect calcium salts in spinach, cheeses, and wines.

Smell is the last special sense to review.

Olfactory receptors are sensory fibers of the olfactory nerve, cranial nerve I. They lie in the olfactory mucosa of the nasal cavity.

These receptors are extremely sensitive, but easily adapt and become fatigued.

Odor-causing chemicals initiate a nerve signal that is interpreted as a specific odor by the brain. Note that olfaction has a strong relationship with emotions and memory.

It is important to realize that all senses are processed and finally perceived in the brain, not in the receptors.

Sensory information is combined to form an overall sensory perception of our world.

For example, flavor is a combination of gustatory and olfactory senses; it can even be affected by other senses, such as touch, pain, and temperature. Nasal congestion interferes with stimulation of olfactory receptors and thereby dulls flavor sensations.

Another example relates to posture and balance: the senses of equilibrium with vision and proprioception combine to help us maintain a safe body position.

Note that some sensory information is processed subconsciously, and like many other functions, our senses may decline as we age.

This concludes the audio review of chapter 10.

9780323871730_Chapter_010.mp3

Chapter_010.rtf

9780323871730_Chapter_010.mp3

Chapter_010.rtf

9780323871730_Chapter_010.mp3