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14 Cards in this Set
- Front
- Back
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What is "long-loop feedback"?
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When the final hormone negatively feeds back all the way to hypothal-pit axis
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What is "short-loop feedback"?
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When the pituitary hormone negatively feeds back on the hypothalamus
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What is "ultrashort-loop feedback"?
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When the hypothalamic hormone negatively feeds back on the hypothalamus and inhibits its own secretion
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What is an example of ultrashort-loop feedback?
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GHRH inhibits GHRH s/c
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What is an example of positive hormonal feedback?
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just before ovulation estrogen feeds back to stimulate surge of LH/FSH from a/p, which causes more estrogen s/c
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What does the "sensitivity" of a hormone mean?
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the hormone conc that produces 50% of max response
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Is sensitivity increased or decreased by down-regulation?
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decreased (response declines even though hormone levels remain high)
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How does down-regulation occur? What is the purpose?
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by decreasing the number or affinity of receptors; to reduce sensitivity of target tissue when hormone levels are chronically elevated
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How does up-regulation occur? What is the purpose?
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in increasing the number or affinity of receptors; so that tissue will still respond even if the hormone level is depressed
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What are 2 examples of down-regulation?
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progesterone in the uterus down-regulates its own receptors and estrogen receptors
T3 downregulates TRH receptors in the a/p = decreased responsiveness of hyp/pit/thy axis with chronically elevated T3 |
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What are 3 examples of up-regulation?
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prolactin up-reg's receptors in breast
growth hormone up-reg's receptors in skel musc and liver estrogen up-reg's own receptors in uterus (and LH receptors in ovaries) |
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Describe the AC/cAMP mechanism of hormone action
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G protein -> AC -> cAMP -> PKA -> phosphorylation
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Describe the IP3 mechanism of hormone action
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G protein -> phospholipase C -> IP3 (& diacylglycerol) -> Ca release from ER -> PKC -> phosphorylation
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Describe the steroid mechanism of hormone action
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steroid hormone -> nuclear receptor -> exposes DNA binding domain -> transcrip -> translat -> physiologic actions
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