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)