endocrine system Flashcards
coordinates activities of the organ systems
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difference bw endocrine and exocrine glands
endo releaehormoes diretly into body circulation; exocrine–elease hormones transported by ducts
what is the infundibulum?
the slender cord that connects the pituitary gland to the hypothalamus
two types of hormones that the anterior pit produces
direct hormones (act directly on their target organ) and tropic hormones (stimulate other endocrine glands to release hormones)
how is hormonal released regulated for the AP?
• Hormonal secretions oF the AP are regulation by hypothalamic hormones called release/inhibiting hormones or factors
What are the tropic hormones of the AP?
lutenizing hormone, FSH, adrenocorticotropic hormone; thyroid stilumaling hormone
what are the direct hormones of the AP?
prolactin, endorphin, growth hormones (somatotropin), melanocyte-stimulating hormone
what is FSH?
o In women, causes maturation of ovarian follicles
♣ In turn secrete estrogen
In men, stimulates maturation of seminiferous tubules and sperm production
What is LH?
o In women, LH stimulates ovulation and maintenance of the corpus luteum
♣ Also responsible for regulating progesterone secretion in women
o In men, it stimulates interstitial cells of the testes to synthesize testosterone
What is adrenocorticotropin?
o Stimulates adrenal cortex to synthesize and secrete glucocorticoids and is regulated by the corticotropin-releasing factor (CRF)
what is TSH?
o Stimulates thyroid gland to synthesize and released thyroid hormones
Includes thyroxine
what is prolactin?
stimulates milk production in mammary glands
endorphins
These are neurotransmitters that have pain-relieving properties
what is growth hormone?
o Promotes bone and muscle growth
o Promotes protein synthesis and lipid mobilization and catabolism
what is acromegaly?
overprod of GH in ADULTS, where one part of the body continually grows–gigantism occurs when GH is over prod in children (everything grows proportionally large)
what is MSH?
o Secreted by the intermediate lobe of the pituitary
o In mammals, the function of MSH is unclear
o In frogs however, MSH causes darkening of the skin via the induced dispersion of molecules of pigment in melanophore cells
the posterior pit gland does nOT produce hormones; it stores and released them in response to APs descending from the hypothalamus
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hormones of the neurohypophysis
oxytocin, ADH
what is oxytocin?
peptide hormone
♣ Secreted during childbirth
♣ Increases strength and frequency of uterine contractions
♣ Release can also be induced by suckling
♣ Stimulates milk secretion in mammary glands
what is ADH?
peptide hormone-♣ Increase permeability of the nephron’s collecting duct to water; this promotes water reabsorption and increasing blood volume which subsequently increases blood pressure
♣ Secreted when plasma osmolarity increases—as sensed by osmoreceptors in the hypothalamus; or when blood volume decreases as sensed by baroreceptors in the circulatory system
where is the hypothalamus located?
above the pit gland in the forebrain
the hypothalamus • Receives neural transmissions from other parts of the brain and from peripheral nerves that trigger specific responses from its neurosecretory cells–these descend to the pit gland and regulate hormone release via negative feedback
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how does the hypothalamus interact with the AP?
hypothalamic-released hormones stimulate to inhibit the release of hormones from the AP; e.g.–GnRH stimulates the release of LH and FSH; GnRH is released from the hypo and travels through the hypothalamus-hypophyseal portal system–>reaches the AP right away
describe the feedback pathway that regulates corticosteroid levels in the blood
when corticosteroid levels drop, the hypothalamus is signaled to released corticotropin-releasing factors into the portal system; these hormones then act on the AP to release ACTH; in turn, this ACTH tells adrenal glands to release more glucocorticoids; when plasma concentration of corticosteroid levels are high enough, they exhibit an inhibitor effect on the hypothalamus
interaction of the hypothalamus with the NH/PP
neurosecretory cells in the hypothal synthesize and secrete peptide hormones oxytocin and ADH and send them to the PP down their axons for storage and further secretions
• Thyroid hormones affect the function of nearly every organ system in the body
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how do thyroid hormones affect children?
In children, these hormones are essential for growth and neurological development
how do thyroid hormones affect adults?
In adults, these hormones increase the rate of metabolism throughout the body and are essential for maintenance of metabolic stability
what are the thyroid hormones?
thyroxine (T4) and triiodothyronine (T3)
How are T3 and T4 formed?
from the glycoprotein thyroglobulin in thyroid cells
o Because of the specific tertiary structure of the glycoprotein from which T3 and T4 are formed, iodinated tyrosine residues present in thyroglobin are able to bind together to form active thyroid hormones
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T3 is 5x more potent than T4
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unbound T3 an T4 can go into cells and elicit a response–but 99.5% of T3 and T4 are bound to plasma proteins
learnt this in tox hollaaaaa
where are T4 and T3 formed?
All T4 is formed in the thyroid gland, whereas only 20% of T3 is–>the rest of T3 is formed by conversion of T4–>T3 via 5’ monodeiodase
where is monodeiodase normally found?
in all peripheral tissues
what is hypothyroidism, the symptoms, and treatment?
thyroid hormones undersecreted or not at all; symptoms: slower heart, weight gain, slow respiratory rate, fatigue, cold intolerance; treatment–supplement thyroid hormones from synthetic or animal-derived products
what is hyperthyroidism, the symptoms, and treatment?
thyroid is overstimulated, thyroid hormones oversecreted ; symptoms: increased metabolic rate, feeling excessively warm, profuse sweating, palpitations, weight loss, protuding eyes; treatment: substances that inhibit thyroid hormone release or ablation of thyroid with radiation
• Calcitonin
o Decreases plasma Ca2+ concentrations by inhibiting the release of Ca2+ from bone
o Secretion is regulated by plasma Ca2+ levels
o Antagonistic to parathyroid hormones
• In both disorders, thyroid often enlarges
o This forms a bulge on the neck called a goitre
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What are the parathyroid glands, and what do they do?
four small pea-shaped glands embedded in the posterior surface of the thyroid; they synthesize and secrete parathyroid hormone (PTH)
what is PTH and what does it do?
parathyroid hormone; regulates plasma Ca2+ conc by stimulating Ca release from the bone and inhibiting Ca2 excretion from the kidneys
what is the issue with breaking bone down to release Ca?
it also releases phosphate–>parathyroid compensates for this by stimulating the excrement of phopshate by the kidneys
o In response to stress, adrenocorticotropic hormone (ACTH—produced by the AP) stimulates the adrenal cortex to produce more than two dozen different steroid hormones
♣ Are collecting known as adrenocortical steroids or corticosteroids
♣ In the blood stream, they corticosteroids are bound to transport proteins
• Called transcortins
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how do corticosteroids regulate?
determine which genes are transcribed and at what rate–will change the amount of proteins in the cell and affect metabolism along with other things
what are the major classes of corticosteroids?
glucocorticoids, mineralcorticoids, cortical sex hormone–>all secreted by the adrenal cortex
what is the role of glucocorticoids, how do they exert their effect, and give an example
they regulate blood glucose levels and protein metabolism; raise BGL by promoting protein metabolism and gluconeogenesis; also inhibit protein synthesis; release amino acids from skeletal muscle and lipids from adipose tissue as well as promote use of lipids and have anti-inflammatory effects; e.g. cortisol and cortisone
what is the role of mineralcorticoids, how do they exert their effect, and give an example
regulate K and Na levels in the blood; –>consequently, this regulates plasma/total ECF volume; e.g. aldosterone–>causes active reabsorption of sodium and passive reabsorption of water into the nephron of the kidney; results in both an inceased ECF and blood pressure; excess aldosterone causes fluid retention and high blood pressure (hypertension); mineralcorticoids activated by angiotensin II (peptide hormone) and inhibited by ANP (atrial naturetic peptide)
what is the role of cortical sex hormone, how do they exert their effect, and give an example
e.g. androgens; androgens (such as androstenedione or dehydroepiadrosterone) secreted by the adrenal cortex in both men and women; in men, androgens are mostly secreted b ythe testes, so androgens secreted b ythe AC have negligible efffects; for women, excess androgen released causes masculinizing effects
What hormones does the adrenal medulla secrete?
epinephrine (adrenaline) and norepinephrine (noradrenaline)
E/A, and NE/NA both belong to classes of amino-acid derived compounds called catecholamines
ya
what is the role of epinephrine?
stimulates the conversion of glycogen to glucose in skeletal muscle (and liver tissue) (causes an increase in BGL and basal metabolic rate)
• Both E and NE increase the rate and strength of the heartbeat and dilate and constrict blood vessels in such a way as to increae the blood supply to the skeletal muscle, heart, and brain
o While decreasing the blood supply to the kidneys, skin, and digestive tract
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• Both E and NE will also promote the release of lipids by adipose tissue
ya
• These effects are known as the fight or flight response
o Elicited y the sympathetic NS in response to stress
• Epinephrine will also inhibit other functions that are not immediately important for survival
o E.g digestion
• Both E and NE are neurotransmitters
Proteins used by neurons to transit signals
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what are the two functions of the pancreas?
exocrine and endocrine
what is the exocrine function of the pancreas?
performed by cells secrete digestive enzymes into small intestine via a series of ducts
what is the endocrine function?
performed by small glandular structures called islets of langerhans–>composed of alpha and beta cells; alpha cells produce and secrete glucagon while beta cells epinephrine;
both glucagon and insulin are protein hormones?
ya
what is the most common endocrine disorder?
diabetes mellitus
what is the role of pineal glands and where are they found?
tiny structures found at the base of the brain; secrete the hormone melatonin which is believed to play a role in circadian rhythms
how is melatonin secretion regulated?
by light and dark cycles
• in primitive vertebrates, melatonin ightens the skin by concentrating pigment granules in melanophores (melatonin is antagonistic to MSH)
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how does the kidney compensate for blood volume loss?
produce renin–enzyme that converts plasma angiotensin to ang I->converts to ang II; ang II stimulates arendal cortex to secrete aldosterone; this helps restore BVL by increasing sodium reabs. by the kidneys which leads to an increase in BVL and an inhibition of the productions of renin
what hormones/hormone regulators do the kidneys produce?
renin and erythroprotien (EPO)
what is erythroprotein?
a glycoprotein which stimulates RBC production; stimulates stem cells to differentiate into rubriblasts (increases rate of mitosis); increases the rate of reticulocyte release from bone marrow; and increases Hb formation, which is critical for the maturation of RBC at a rapid rate
what are the hormones produced and secreted by gastrointestinal glands?
gastrin, secretin, cholecystokinin
role of gastrin
ingestion food stimulates the release; carried to gastric glands and stimulates glands to secrete HCl
role of secretin
released by the small intest. when acidic chyme enters from the stomach; stimulates release of HCO3- from the pancreas which will neutralize the chyme
role of cholecystokinin
released by the samll intest. in response to fats; causes the contraction of the gallbaldder to release bile into the small intestine (emuslifer–dissolves very lipid sol stuff)–bile is NOT a hormone
classes of hormones
peptide and steroid
peptide hormones
small, simple amino acid chains such as ADH, to complex chains such as insulin–act as FIRST MESSENGERS;
o When they bind to specific receptors on the surface of their target cell, they trigger a series of enzymatic reactions within the cell
♣ The first of the reactions may be the conversion of ATP to cyclic AMP
• Catalyzed by the membrane-bound enzyme adenylate cyclase
YA
cyclic AMP
acts as second messenger; relays messange from extracell peptide hormone to cytoplasmic enzymes; causes series of reactions in a cell–> cascade effect, amplified at each step; cAMP deactivated by phosphodiesterase
steroid hormones
e.g. aldosterone or estrogen; lipid derived molecules and contain characteristic ring structures; produced by testes and ovaries as well as adrenal cortex; hydrphobic–>go right through membrane, act directly n target receptors; receptor-hormone complex enters nucleus and directs transcription and translation; directly activates gene expression by binding to receptors on chromatin
