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Endocrine Physiology > Hypothalamus and Pituitary > Flashcards

Hypothalamus and Pituitary Flashcards

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?

A

3 minutes

20
Q

diabetes insipidus

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

A

excessive AVP prevents water from being excreted

often caused by cancer

22
Q

what is the stimulus for oxytocin release

A

suckling at the breast

genital stimulation- (may increase ejaculatory response in males)

23
Q

what are the different effects of oxytocin?

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

A

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

25
Q

what is the pattern of release for the HHS hormones?

A

pulsatile/episodic- seems to maintain an optimum number of receptors on pituitary cells

26
Q

what are the anterior pituitary receptors

A

activators of cAMP, cGMP, PIP

27
Q

describe the characteristics of the HHS

A

small neurons, short tract, little storage, short vascular pathway

28
Q

what are the 3 subtypes of hormones produced in the anterior pituitary?

A

POMC polypeptides
glycoproteins
somatomammotropic proteins

29
Q

describe POMC construction

A

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
Q

ACTH functions

A

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
Q

when is plasma ACTH lowest? highest?

A

6-11 pm

6-8 am

32
Q

which portion of ACTH is important for binding?

A

11-24

33
Q

which portion of ACTH is important for its effects?

A

4-10

34
Q

what are the regulatory factors for ACTH?

A

negative- cortisol at hypo and pit

positive- CRH from hypo
urocortins from hypo
neuro- pain/anxiety

35
Q

melanocyte stimulating hormones

A

creates an a and b that share sequences of ACTH. a is stronger

36
Q

MSH regulatory factors

A

positive- MSH releasing factor (MRF) from hypo
neuro- pain/anxiety
CRH from hypo

negative- cortisol at hypo
MIF from hypo

37
Q

endorpines

A

POMC peptide- b-endorphin- lowers body temp, produces analgesia and catatonia

38
Q

describe the structure of glycoprotein hormones

A

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
Q

thyroid stimulating hormone

A

acts on thyroid to produce thyroid hormones

stimulates cellular growth

40
Q

regulation of TSH

A

negative- T3 at pituitary

positive- TRH and thyroliberin from hypothalamus

neural

41
Q

FSH function

A

gametogensis in testes,

follicle growth and estrogen synthesis in ovary

42
Q

LH function

A

induces testosterone production from Leydig (interstitial)

matures follicles to corpora lutea
estrogen and progesterone production

43
Q

FSH and LH regulation

A

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
Q

human chorionic gonadotropin effects

A

maintains corpus leuteum during early pregnancy- maintains estrogen and progesterone production during first trimester

45
Q

prolactin effects

A

initiation of lactation (secretion)

46
Q

prolactin regulation

A

negative- PIF (dopamine) from hypo

positive- TRH from hypo
estrogens at hypo and pit

neuro- suckling inhibits PIF from hypo

47
Q

how is prolactin regulation different than all other anterior pituitary hormones?

A

it is inhibited by the hypo

Endocrine Physiology (5 decks)

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