Human Physiology Unit 2 Exam
dejavu123
OpenStax_Physiology_CH17_ImageSlideshow1.pptxPHYSIOLOGY
Chapter 17 THE ENDOCRINE SYSTEM
PowerPoint Image Slideshow
College Physics
Chapter # Chapter Title
PowerPoint Image Slideshow
Long-distance signaling
Nervous system – uses electrical or chemical signals that result in quick response and short-term actions. External stimulus.
Endocrine system – chemical signals only = hormones; transported through blood, bind to target cells to effect a response.
May be quick such as epinephrine, or slow such as reproductive hormones.
Many hormones work at different receptor sites to produce different reactions at each site.
Response to internal stimuli to regulate homeostasis.
Endocrine gland
Endocrine glands are ductless glands that secrete hormones into surrounding interstitial fluid. These are then picked up by the blood and transported throughout body.
Examples: Pituitary, adrenal, thyroid, parathyroid, pancreas.
Many other organs and tissues have some endocrine function.
Endocrine = hormone enters blood or lymph and acts far away
Autocrine = some hormones act on the cells that secrete them
Paracrine = hormones that mainly stay local but act on cells other than themselves
Can only affect their target cells due to the specificity of receptors.
Basic types of hormones
Amine – modification of amino acid tyrosine or tryptophan eg. Melatonin
Peptide and Protein – chains of amino acids eg. Catecholamines, thyroid hormones, ADH, Growth hormone
Steroid Hormone – derived from cholesterol, insoluble in water so must travel with a protein carrier eg. Aldosterone, reproductive hormones, cortisol
Pathways of hormone action
Binding of Lipid-Soluble Hormones
A steroid hormone directly initiates the production of proteins within a target cell.
Steroid hormones diffuse through the cell membrane.
The hormone binds to its receptor in the cytosol, forming a receptor–hormone complex.
The receptor–hormone complex then enters the nucleus and binds to the target gene on the DNA.
Transcription of the gene creates a messenger RNA that is translated into the desired protein within the cytoplasm.
Pathways of hormone action
Binding of Water-Soluble Hormones
Water-soluble hormones cannot diffuse through the cell membrane.
Bind to a surface cell-membrane receptor. The receptor then initiates a cell-signaling pathway within the cell involving G proteins, adenylyl cyclase, the secondary messenger cyclic AMP (cAMP), and protein kinases.
Protein kinases phosphorylate proteins in the cytoplasm. This activates proteins in the cell that carry out the changes specified by the hormone.
Target cell response and regulation
Down Regulation – If there is too much hormone, cells decrease production of receptors to maintain normal levels of activity.
Up Regulation – If there is too little hormone, cells will make more receptors to trap all the hormone they can.
Permissive – cell must have more than one hormone present to allow activity of hormone(s). Eg. Thyroid and reproductive hormones
Synergistic – two with similar actions combine to amplify the response eg. FSH and estrogen
Antagonistic – hormones with opposing effect eg. Insulin and glucagon
Positive feedback loop – more = more
Negative feedback loop – more = less
Command center complex
Hypothalamus–Pituitary Complex
Secretes several hormones itself
Secretes hormones that regulate other hormones
Coordinates messages between endocrine and nervous system
Pituitary gland
Anterior Pituitary
Glandular in origin
Secretes 7 hormones
Posterior Pituitary
Neural in origin. An extension of the hypothalamus
Stores and releases 2 hormones produced by the hypothalamus
Posterior pituitary hormones
Oxytocin
Stimulates uterine contractions through positive-feedback mechanism
After childbirth, responsible for the milk-ejection reflex
Parent-newborn bonding
Sexual response
ADH or vasopressin (due to vasoconstriction)
An increase in blood osmolarity, primarily Na+, releases ADH. Acts on collecting ducts in kidney to open aquaporin channels and to resorb water back into the bloodstream.
Negative-feedback system
Alcohol inhibits ADH, thus allowing kidney to dump water. Creates dehydration and a hangover.
Diabetes Insipidus – underproduction of ADH.
Anterior pituitary hormones
Anterior pituitary actually makes the hormone but the hypothalamus controls the release through a stimulating hormone or an inhibiting hormone.
Growth hormone/ somatotropin
Promotes protein synthesis and tissue building
Controlled by GHRH and GHIH from the hypothalamus
Stimulates lipolysis in cells for ATP production and stimulates liver to break down glycogen. Both increase blood glucose.
Stimulates insulin-like growth factor from liver, increasing cell proliferation and protein synthesis especially in skeletal muscle and cartilage.
Gigantism = too much GH in children
Acromegaly = too much in adults, causes bones of face, feet and hands to grow.
GH deficiency/pituitary dwarfism = too little GH
Anterior pituitary hormones
Thyroid Stimulating Hormone (TSH)
Regulated by TRH from the hypothalamus
Regulates thyroid gland production of thyroid hormones through negative-feedback loop.
Synthesis of T3 and T4
TSH binds to cells of thyroid gland causing cell to take up iodide from the blood.
Inside the cell, iodide is oxidized to iodine and moved into colloid, a matrix surrounded by and produced by follicle cells.
In colloid, iodine is attached to the amino acid tyrosine in the protein thyroglobulin. Thyroglobulin may have one iodine or two. Thyroglobulins are then paired so the whole unit has either 3 iodines, T3, or 4 iodines, T4.
Anterior pituitary hormones
TSH cont’d.
T3, T4 are released into the blood. Most are bound to protein carriers. Free T3,T4 can move into cells to
Influence basal metabolic rate
Bind to mitochondria to increase ATP production. This increased production is inefficient and therefore much heat is released
Increase cells’ sensitivity to catecholamines – increases HR and BP
Hypothyroidism – Usually due to insufficient iodine in the diet. TSH increases, results in accumulation of thyroglobulin and colloid thus increasing the size of the thyroid gland = goiter.
Hyperthyroidism – Increase in T3,T4 usually as a result of a pituitary or thyroid tumor. Grave’s disease is autoimmune stimulation resulting in a goiter.
Hypothyroidism with goiter
Goiter
(credit: “Almazi”/Wikimedia Commons)
Anterior pituitary hormones
Thyroid gland also produces Calcitonin.
Increased Ca++ in the blood causes thyroid gland to release calcitonin. This results in
Decreased osteoclast activity
Increased osteoblast activity
Increase loss of Ca++ through urine
Parathyroid glands produce parathyroid hormone (PTH)
Released when Ca++ blood levels fall
Increases osteoclast activity, Ca++ resorption from the kidney, and absorption of dietary Ca++ from the gut.
Hyperparathyroidism – too much PTH, results in decreased bone density, may result in spontaneous fractures and/or Ca++ deposits in soft tissue
Hypoparathyroidism – affects Na+ balance thus muscles
Anterior pituitary hormones
Adrenocorticotropic Hormone (ACTH)
The hypothalamus releases Corticotropin-releasing hormone (CRH) that causes the pituitary to release ACTH.
ACTH is derived from a precursor molecule Pro-opiomelanotropin (POMC).
POMC also is a precursor to melanocyte-stimulating hormone and the endorphins, endogenous opioids that suppress pain.
ACTH acts on the Adrenal Gland in response to stress.
Cortex of the adrenal gland made up of three layers
Produces mineralocorticoids – aldosterone
Produces glucocorticoids – cortisol
Produces androgens
Medulla is an extension of the Autonomic Nervous System and produces catecholamines.
Anterior pituitary hormones
Adrenal gland, cont’d.
Cortex is a component of the Hypothalamus-pituitary-adrenal axis (HPA)
Function is to respond to stress through the HPA axis by regulating BP, BV, Fluid and electrolyte balance and long-term stress.
Mineralocorticoids – affect minerals especially Na+ and K+ to control fluid and electrolyte balance
Aldosterone – major mineralocorticoid. A decrease in Na+ in the blood causes the release of aldosterone to reabsorb Na+ in the kidney and ultimately water to increase BP and BV. Also, part of the Renin-Angiotensin-Aldosterone system. Angiotensin II signals the cortex to release aldosterone
Glucocorticoids – named thus due to their role in glucose metabolism
Cortisol – released as a result of long-term stress. Inhibits tissue building while increasing the breakdown of glycogen, triglycerides, and muscle protein into fuel. Also decreases the immune response to inflammation.
Anterior pituitary hormones
Adrenal gland cont’d.
Androgens – Supplemental sex/reproductive hormones. In the tissue they are converted to testosterone and estrogens.
The medullary tissue is composed of SNS neurons and is responsible for the release of catecholamines in response to short-term stress – Fight or Flight
General Adaptation Syndrome – how the body responds to stress; acute, chronic or both.
Alarm reaction – short-term, Fight or flight, catecholamines released from the medulla
Stage of resistance – when short-term is not relieved, body tries to compensate for the stress. Starving? Increase more nutrients from the gut…
Stage of exhaustion – decompensation or can’t compensate any longer. Physical and psychological results….
Anterior pituitary hormones
Disorders of ACTH
Cushing’s disease – too much cortisol, increased blood glucose, localized accumulation of fat, rapid weight gain. Result of pituitary tumor?
Addison’s disease – not enough cortisol. Decreased Na+ and BG. Symptoms are vague and so is cause.
FSH and LH – follicle stimulating hormone and luteinizing hormone. Reproductive hormones released during puberty in response to GnRH from hypothalamus.
FSH stimulates the production and maturation of gametes (ova and sperm)
LH stimulates ovulation, estrogens and progesterone production in females and testosterone in males.
Prolactin – promotes development of breast tissue and milk production
Gonadal and placental hormones
Testes produce testosterone – responsible for development of male reproductive tract and secondary sex characteristics. Ovary produces it also.
From ovary : Estrogens – responsible for development of female reproductive tract and secondary sex characteristics, regulates menstrual cycle, maintains pregnancy
Progesterone – regulates menstrual cycle, preps for and maintains pregnancy.
Placental hormones –
Human chorionic gonadotropin (hCG) – promotes progesterone synthesis to maintain pregnancy,
Placental lactogen – prepares for lactation
Relaxin – softens ligaments and widens pelvis
Intermediate pituitary hormone
Melanocyte-stimulating hormone
Derived from POMC
Local production in the skin to increase melanin production in response to UV light
MSH from hypothalamus decreases appetite and contributes to sexual arousal.
Pineal Gland
Cells secrete melatonin to regulate circadian rhythm.
Secretion varies according to light levels from the environment.
Light stimulates non-photoreceptor retinal cells. More light = less melatonin, Less light = more melatonin.
Pancreas
Exocrine portion secretes digestive enzymes into small intestine.
Endocrine portion secretes hormones into bloodstream.
Pancreatic islets – cells that secrete glucagon, insulin, somatostatin, and pancreatic polypeptide (PP)
α cells – produce glucagon in response to low blood glucose levels
1. Stimulates liver to breakdown glycogen and release glucose into blood.
2. Stimulates liver to convert amino acids into glucose = gluconeogenesis.
3. Stimulates lipolysis to release glucose for energy = gluconeogenesis
Pancreas
β cells – produce insulin when BG is high
Activates a receptor on cell membrane that moves glucose transporters to the cell membrane surface allowing cell to take in glucose for ATP production.
Stimulates the liver to turn extra glucose into glycogen for storage.
Δ cells – release somatostatin that inhibits both glucagon and insulin.
PP cells – secrete PP hormone to control appetite.
Disorders of the Pancreas
Diabetes mellitus –
Type I – autoimmune, affects β cells, no insulin produced
Type II – cells of the body are resistant to insulin, β cells make more and more insulin and finally become exhausted. At this point patient may need injectable insulin.
This OpenStax ancillary resource is © Rice University under a CC-BY 4.0 International license; it may be reproduced or modified but must be attributed to OpenStax, Rice University and any changes must be noted.
