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Endocrine Physiology > Hypothalamus and Pituitary > Flashcards

Hypothalamus and Pituitary Flashcards

(47 cards)

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1
Q

describe the location of the hypothalamus

A

bounded:
anteriorly- optic chiasm and supraoptic nuclei
laterally- optic tracts and medial forebrain bundles
posterior- mammillary bodies

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2
Q

where are the paraventricular neurons?

A

adjacent to the 3rd ventricle, most dorsal nuclei in hypothalamus

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3
Q

hypothalamic supraoptic-paraventricular-neurohypophysial tract

A

large neurons extending SON and PVN w/ axons terminating near blood vessels in neural lobe

responsible for synthesis and release of oxytocin and vasopressin

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4
Q

hypothalamic hypophysiotropic tract

A

smaller, diffuse neurons of medial basal hypothalamus that terminate in median eminence and proximal pituitary stalk, adjacent to capillary plexus hypophysial portal system

neurons are the source of releasing factors/hormones

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5
Q

hypophysial portal system

A

receives signals from HHS tract, w/in proximal pituitary stalk

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6
Q

how are oxytocin and AVP different?

A

they have different amino acids at the 3 and 8 position

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7
Q

vasopressin effects

A

potent anti-diuretic by acting on DCT and CT in kidneys

vasopressor, w/ minor milk ejection effects. arginine AVP is found in humans

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8
Q

ddAVP

A

therapeutic AVP analog that acts as diuretic but does not produce vasoconstriction

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9
Q

what are the products in terminals of AVP and oxytocin

A

AVP- AVP, VP-associated neurophysin, and glycopeptide

oxytocin- oxytocin, OT associated neurophysin

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10
Q

why doesnt OT have a glycopeptide?

A

they come from the same precursor except the OT has a stop codon, leaving only a histidine

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11
Q

OT and AVP are not bound to plasma proteins

A

ok

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12
Q

what signals the release of OT and AVP secretory products

A

Ca from an AP

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13
Q

where are the precursors of OT and AVP cleaved?

A

inside the secretory vesicles

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14
Q

how does AVP cause water retention?

A

acts on V2 receptors (on blood side), producing a rise in cAMP, resulting in the addition of a luminal pore (aquaporin 2)

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15
Q

what is the receptor for AVP that results in vasoconstriction?

A

V1a

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16
Q

what is the receptor for AVP that regulates ACTH release?

A

V1b- acts in concert w/ CRH

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17
Q

what is the major regulator of AVP release

A

increase in osmolality sensed by osmoreceptors in anterior hypothalamus (near SON and PVN)

about 10% reduciton in blood elicits ADH release

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18
Q

describe some non-osmotic regulators of AVP

A

atrial stretch receptors- inhibit AVP (lack of signal releases AVP)

carotid and aortic sinus- inhibit AVP

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19
Q

how long is the AVP half life?

20
Q

diabetes insipidus

Study These Flashcards
A

central- no AVP produced
nephrogenic- no AVP receptors

results in drinking lots of water and voiding lots of dilute urine

treated w/ thiazide diuretics

21
Q

SIADH

Study These Flashcards
A

excessive AVP prevents water from being excreted

often caused by cancer

22
Q

what is the stimulus for oxytocin release

Study These Flashcards
A

suckling at the breast

genital stimulation- (may increase ejaculatory response in males)

23
Q

what are the different effects of oxytocin?

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A

milk let down hormone- contraction of myoepthelial and smooth cells

uterine contraction at birth (only w/ fully dilated cervix)

improves socialization, decreases aggression, reduces anxiety

24
Q

describe the effect of progesterone on OT

Study These Flashcards
A

progesterone inhibits OT in the uterus. Pg levels decline at the end of pregnancy, perhaps allowing OT to exert effects on uterus

25
what is the pattern of release for the HHS hormones?
pulsatile/episodic- seems to maintain an optimum number of receptors on pituitary cells
26
what are the anterior pituitary receptors
activators of cAMP, cGMP, PIP
27
describe the characteristics of the HHS
small neurons, short tract, little storage, short vascular pathway
28
what are the 3 subtypes of hormones produced in the anterior pituitary?
POMC polypeptides glycoproteins somatomammotropic proteins
29
describe POMC construction
all derived from a common precursor molecule and cleaved by intravesicular enzymes to form different peptides which cells form which peptides is determined by which proteases they contain (somewhat determined by cell location)
30
ACTH functions
binds receptors in zona fasciculata and zone reticularis to increase production of glucocorticoids- cortisol also converts cholesterol to prenenolone to initiate steroidogenesis these actions are mediated through cAMP trophic effects
31
when is plasma ACTH lowest? highest?
6-11 pm | 6-8 am
32
which portion of ACTH is important for binding?
11-24
33
which portion of ACTH is important for its effects?
4-10
34
what are the regulatory factors for ACTH?
negative- cortisol at hypo and pit positive- CRH from hypo urocortins from hypo neuro- pain/anxiety
35
melanocyte stimulating hormones
creates an a and b that share sequences of ACTH. a is stronger
36
MSH regulatory factors
positive- MSH releasing factor (MRF) from hypo neuro- pain/anxiety CRH from hypo negative- cortisol at hypo MIF from hypo
37
endorpines
POMC peptide- b-endorphin- lowers body temp, produces analgesia and catatonia
38
describe the structure of glycoprotein hormones
all have an a and b chain held together by non covalent bonds and have carb side groups a chain of LH, FSH, and TSH are identical (hCG has additional AAs). responsible for activating hormone-receptor complex b is unique- specificity
39
thyroid stimulating hormone
acts on thyroid to produce thyroid hormones stimulates cellular growth
40
regulation of TSH
negative- T3 at pituitary positive- TRH and thyroliberin from hypothalamus neural
41
FSH function
gametogensis in testes, follicle growth and estrogen synthesis in ovary
42
LH function
induces testosterone production from Leydig (interstitial) matures follicles to corpora lutea estrogen and progesterone production
43
FSH and LH regulation
positive- 1 GnRH (LHRH, LRF, LHRF, gonadoliberin) from hypo 2 estrogen at hypo and pituitary prior to ovulation (LH surge) negative 1 estrogen from corpus luteum and follicle at hypo and pituitary 2 testosterone (as estradiol) at hypo and pituitary 3 inhibin produced by sertoli cells/ follicle 4 CNS
44
human chorionic gonadotropin effects
maintains corpus leuteum during early pregnancy- maintains estrogen and progesterone production during first trimester
45
prolactin effects
initiation of lactation (secretion)
46
prolactin regulation
negative- PIF (dopamine) from hypo positive- TRH from hypo estrogens at hypo and pit neuro- suckling inhibits PIF from hypo
47
how is prolactin regulation different than all other anterior pituitary hormones?
it is inhibited by the hypo

Endocrine Physiology (5 decks)

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