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87 Cards in this Set
- Front
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classification of adenohypophyseal hormones
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somato-lactogen group
two-subunit group proopiomelanocortin |
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somato-lactogen group
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prolactin/leuteotropin
growth hormone/somatotropin placental lactogen |
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placental lactogen
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not a pituitary hormone but structurally similar to PRL & GH
synthesized in placenta only during pregnancy |
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two-subunit group
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leuteinizing hormone
follicle stimulating hormone thyroid stimulating hormone |
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proopiomelanocortin
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large precursor protein broken down into ACTH
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chemistry of GH
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190 aas
20 kDA = effectively filtered by the kidneys 4 a-helices |
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hypothalamic control of GH
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mediated by regulation of cyclic-AMP at median eminence
GH-RH GH-RIH/somatostatin |
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negative feedback regulation of GH
inhibition of GH-RH |
increased blood GH levels
IGF-I inhibits GH-RH and stimulated GH-RIH |
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physiological down regulation of GH
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glucose
stress |
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physiological up regulation of GH
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aas
exercise sleep ADH ghrelin ( secreted from gut after meal ) |
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Transportation of GH in plasma
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released in short bursts, bind to carrier protein to stabilize conc of GH according to equilibrium
only free GH is released from blood |
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GH Mechanism of Action
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1)direct effects on target tissues
2)indirect effects on target tissues |
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GH direct effects on target tissues
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stimulated target tissues synthesize and release IGF-I
liver-synthesized IGF-I acts on pituitary gland in negative feedback loop |
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GH indirect effects on target tissues
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via IGF-I produced by direct target tissues
ie. bone growth |
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GH biochemical mechanism of action
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GH binds two plasma membrane GH-receptors activing the JAK/STAT pathway
regulates expression of GH-specific genes |
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biological actions of growth hormone
ie. What does Growth Hormone do to the body? |
effects on:
bone growth carbohydrate metabolism lipid metabolism protein metabolism mammary gland matabolism |
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growth hormone effects on bone growth
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classically mediated by IGF-I
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growth hormone effects on protein metabolism
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growth hormone promotes uptake and synthesis of proteins
"protein-sparing" effect increased protein = increased nitrogen content |
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growth hormone effects on carbohydrate metabolism
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glucose-sparing, antagonizing the use and uptake of glucose
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growth hormone effect on lipid metabolism
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releases lipid from adipocytes to be metabolized
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growth hormone effects on mammary gland metabolism
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auguments/stimulates lactation
indirectly mediated by IGF-I BST= recombinant bovine somatotropin given to dairy herds, controversial |
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chemistry of prolactin
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200 aas
22 kDa similar structure to GH, 4 a-helices |
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placental prolactin
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produced by placenta only during pregnancy
shuts down pituitary production of PRL |
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pituitary synthesis of PRL
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majority of synthesis of PRL
other sources are not significant contributors |
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hypothalamic regulation of PRL
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dopamine "prolactin release-inhibiting hormone"
thyrotropin-releasing hormone |
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effect of dopamine on PRL production
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"brake" or suppress
PRL in constant state of suppression via Prolactin Release-Inhibiting Hormone |
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effect of thyrotropin-releasing hormone on PRL production
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"accelerator" or simulator
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feedback regulation of PRL
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PRL inhibits synthesis
acting on hypothalamus and adenohypophysis |
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physiological regulation of PRL
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steroids
suckling response pregnancy |
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effect of steroids on PRL production
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estrogen stimulates pituitary synthesis & secretion considerably
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effect of suckling response on PRL production
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stimulates brain to increase prolactin levels
increases amount of food for baby and maintain breast function |
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effect of pregnancy on PRL production
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placental prolacting feedbacks to hypothalamus and adenohyphophysis to suppress pituitary prolactin production
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transportion of PRL in blood
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no carrier protein
low circulating levels in males, higher in females highest during pregnancy and lactation |
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PRL mechanism of action
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binds a pair of prolactin-receptors at plasma membrane, activating JAK/STAT pathways
increase in prolactin gene expression |
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biological actions of prolactin
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mammary growth and lactation
rodent corpus luteum male reproductive system |
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effect of PRL on mammary growth and lactation
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stimulate initiation of lactation
stimulate maintenance of lactation in some species |
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effect of PRL on rodent corpus luteum
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stimulates corpus luteum to produce progesterone
"luteotropic hormone" |
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effect of PRL on male reproductive system
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maintains accessory sex glands
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effect of PRL in birds
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maintains crop sac biology
crop: where crop milk is made |
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effect of PRL in fish
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high concentration of PRL-receptors in fish kdiney cell membranes
alters function of kidney when transitioning between fresh and salt water to adjust to new saltity |
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placental lactogens
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species specific
biological activities more similar to GH in some species and PRL in other species NOT a pituitary hormones; produced by placenta during pregnancy |
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chemistry of thyroid stimulating hormone
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a-subunit = 89aa
b-subunit = 112 aas 29 kDa glycoprotein 1% sialic acid |
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hypothalamic control of TSH
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thyrotropin-releasing hormone
somatostatin |
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effect of thyrotropin-releasing hormone on thyroid stimulating hormone production
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acts from hypothalamus on adenohypophysis to increase production and secretion of thyroid-stimulating hormone
(also stimulates PRL release) |
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effect of somatostatin on thyroid stimulating hormone production
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decreases TSH release from adenohypophysis
(also decreases GH release) |
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feedback regulation of TSH
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T3 & T4 act on hypothalamus to diminish TRH production, thus diminishing TSH production
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physiological up regulation of TSH
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cold stress
estrogens |
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physiological down regulation of TSH
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glucocorticoids
GH |
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transportation of TSH in blood
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NO carrier protein
half life = 75 min |
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TSH mechanism of action
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binds 1 plasma membrane receptor, activing G-protein, which activates adenylate cyclase
ATP converts it to cyclic-AMP, activing a protein kinase to modulate TSH gene expression |
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biological effects of TSH
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stimulate synthesis and secretion of thyroid hormones (multi-step process)
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chemistry of FSH
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a-subunit = 89 aas
b-subunit = 115 aas 29 kDa glycoprotein 5% sialic acid (longer 1/2 life) |
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hypothalamic control of FSH
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gondadotropin releasing hormone (GnRH)
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effect of inhibin on FSH production
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produced by gonadal tissues in both males and females for the purpose of reducing pituitary response to gonadotropin-releasing hormone
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effect of estrogen on FSH production
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in females, can stimulate or depress FSH secretion via hypothalamus
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physiological regulation of FSH
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closely regulated by neural input:
females: cyclic activity males: noncyclic activity |
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transport of FSH in blood
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NO carrier protein
half life = 3 - 4 hours |
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FSH mechanism of action
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bind and activate FSH-receptor, activating G-protein, stimulating ATP conversion of adenylate cyclase into cyclic-AMP, stimulating a protein kinase and gene transcriptions
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biological effect of FSH
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effects on ovary
effects on testis |
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effect of FSH on ovaries
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stimualate development of primary follicle
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effect of FSH on testis
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stimulate spermatogenesis and growth of the seminiferous tubules
stimulates production of angroden-binding protein from sertoli cells |
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feedback regulation of FSH
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inhibin
estrogen |
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chemistry of luteinizing hormone
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29 kDa
a-subunit = 89 aas b-subunit = 115 aas 1% sialic acid (shorter 1/2 life) |
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hypothalamic control of LH
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gonadotropin-releasing hormone (GnRH)
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molecules which feedback regulate LH in males
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testerone inhibits LH secretion
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molecules which feedback regulate LH in females
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during follicular phase:
estrogen stimulates LH secretion during luteal phase: estrogen and progesterone inhibit LH secretion |
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physiological regulation of LH
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neural inputs
(temp, light, environment, etc.) cyclic in females noncyclic in males |
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transportation of LH in blood
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no carrier protein
cyclic range in females can be an order of magnitude |
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how does LH act on cell?
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binds and activates LH-receptor, activing G protein, stimulating conversion of adenylate cyclase in cyclic-AMP by ATP, stimulating protein kinases, controlling gene transcription
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effects of luteinizing hormone on ovary
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1) corpus luteum development
2)progesterone synthesis and secretion by corpus luteum |
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effects of luteinizing hormone on testis
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stimulate testosterone synthesis and secretion
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non-pituitary gonadotropins
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pregnant mare serum gonadotropin
human chorionic gonadotropin |
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proopiomelanocortin is a precursor for...
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ACTH
MSH LPH |
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chemistry of POMC
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29 kDa
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chemistry of ACTH
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31 aas
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chemistry of MSH
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13 aas
cleaved in pars intermedia |
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chemistry of Beta Lipotropin (LPH)
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91 aas
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hypothalamic regulation of POMC
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corticotropin-releasing hormone (CRH)
melanocyte-stimulating hormone-releasing factor (MSH-RF) melanocyte-stimulating hormone release-inhibiting hormone |
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feedback regulation of POMC
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ACTH stimulates adrenal steroids
adrenal steroids feedback regulate hypothalamus to dec. CRH production adrenal steroids feedback regulate adenohypophysis to dec. ACTH production |
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physiologic regulation of POMC
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neural input
ie. stress, cold exposure, pain, emotion, diurnal cycle, hemorrhage, exercise, hypoglycemia, infection, trauma, toxins, etc. |
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transport of ACTH in blood
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no carrier protein
half life = 6-9 min therefore, released in bursts easily filtered by kidneys b/c so small |
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ACTH mechanism of action
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ACTH-bound receptor activates G protein, stimulating c-AMP,
activing side chain cleavage enzyme, converting cholesterol to pregnenolone |
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MSH mechanism of action
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MEESH-bound receptor activates G protein, activing c-AMP
activates side chain cleavage enzyme converts cholesterol to pregnenolone |
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biological actions of POMC molecules
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ACTH acts on adrenal gland
B-LPH acts on adipose tissue MSH acts on melanocytes |
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effect of ACTH on adrenal gland
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stimulates synthesis and secretion of glucocorticoids
glucocorticoids are at highest concentration around time of wakening and bottom out at 3-4 PM in nonnoctural species |
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effects of beta lipotropin hormone on adipose tissues
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stimulates lipolysis from triglycerides
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effect of MSH on melanocytes
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stimulates melanocytes in skin to synthesis and secrete pigment
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