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Endo > Hypothalamus/Pituitary (Physiology) > Flashcards

Hypothalamus/Pituitary (Physiology) Flashcards

1
Q

What does the infundibulum contain?

A

nerves

long portal veins

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2
Q

What are the parts of the ant. pituitary?

A

pars distal is

pars tuberalis

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3
Q

What are the parts of the post. pituitary?

A 
pars nervosa (neural)
psrs intermedia
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4
Q

What do the hypothalamic nuclei synthesize?

A
  1. releasing hormones that regulate secretion of hormones from the anterior pituitary
  2. ADH
  3. OT
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5
Q

What is the median eminance?

A

bottom portion of hypothalamus which contains axon terminals of neurons containing HRH

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6
Q

HRH regulate the ____ pituitary, and are secreted into:

A

anterior

the first capillaries of long portal system

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7
Q

Which lobe is composed of neural secretory tissue?

A

posterior

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8
Q

Which lobe is composed of glandular epithelial tissue?

A

anterior

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9
Q

What hormones are released from the posterior pituitary?

A

OT and ADH

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10
Q

Nerve axons in the posterior pituitary come from what 2 nuclei?

A 
supraoptic (SON)
paraventricular nucleus (PVN)
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11
Q

How are hormones released from the posterior pituitary?

A

hormones are synthesized in the hypothalamus, then released down the hypothalmohypophyseal tract, which terminates near capillaries in the posterior pituitary
(hormones are stored/released here)

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12
Q

What neurosecretory cells secrete OT?

A

SON

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13
Q

What neurosecretory cells secrete ADH?

A

PVN

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14
Q

What is the pars nervosa comprised of?

A
  1. neurosecretory fibers of SON and PVN

2. pituicytes

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15
Q

What is the function of the pars nervosa?

A

release of OT and ADH

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16
Q

In what form are ADH and OT synthesized?

A

larger pro- molecules

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17
Q

What is the structure of ADH and OT?

A

nonapeptides with S-S bridges

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18
Q

How are ADH and OT stored?

A

in granules, with neurophysins I and II

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19
Q

What are the actions of ADH?

A
  1. increased contractility of arterial smooth muscle

2. increased water reabsorption

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20
Q

What are the actions of OT?

A
  1. increased contractility of myoepithelial cells of the mammary glands
  2. increased contractility of uterine smooth muscle
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21
Q

How do myoepithelial cells function?

A

when myoepithelial cells contract, they squeeze the lumen; this ejects mile out of the nipple

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22
Q

What stimulates oxytocin secretion?

A

suckling and dilation of cervix

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23
Q

What stimulates ADH secretion?

A
  1. decreased ECF volume by 5-10%

2. increased osmolarity by 1-2%

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24
Q

Where are osmoreceptors?

A

hypothalamus in the OVLT

organum vasculosum of the lamina terminalis

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25
Q

How does increased ADH affect kidneys?

A
  1. increases water permeability of tubules and ducts

2. increases water reabsorption

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26
Q

How does increasing water ingestion affect ADH?

A

decreases rate of secretion

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27
Q

How does increased ECF volume affect the heart? How does this affect water excretion?

A
  1. increased L atrial stretch
  2. decreased secretion of ADH = decreased permeability of tubules and ducts
  3. decreased water reabsorption = increased excretion
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28
Q

What are the effects of stalk sectioning on the nerve tracts to posterior pituitary?

A
  1. transient polyuria and polydipsia (DI), resulting from accumulation of neurosecretory material proximal to lesion
  2. with time, capillaries adjust to self repair
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29
Q

What does the intermediate lobe (maybe) secrete?

A

MSH

30
Q

What is notable about the hypophyseal portal veins?

A

they are not totally without oxygenation

31
Q

What are the hormones of the ant lobe?

A

ACTH, TSH, LH, FSH, GH, PL

32
Q

What kind of hormones is ACTH? Why is only a portion of this synthesized in artificial forms?

A

peptide

only 20 of the aa are needed for biological activity

33
Q

What does the term “ACTH 1-24” mean?

A

24aa but full activity

34
Q

How do melanophores behave on a light background?

A

melanin granules are kept packed closely in center of cell, so not much light absorption
(frog = light colored)

35
Q

How do melanophores behave on a dark background?

A

MSH causes the mealanin granules to disperse out the long arms of the cell; more light is absorbed and the frog becomes darkly colored
(helps hide from predators, like the huge Highpoint Owl)

36
Q

Why does excess ACTH cause hyperpigmentation?

A
  • -MSH structure lies within ACTH

- -MSH stimulates synthesis of melanin&raquo_space; skin darkens; in excess = hyperpigmentation (worse in creases)

37
Q

How does removal of adrenals affects ACTH?

A

increases, which results in hyperpigmentation

is this right? increased cortisol blocks ACTH via negative feedback; thus no cortisol would = production?

38
Q

What cells in pars distalis are acidophilic?

A

GH (50%)

PRL (15-20%)

39
Q

What cells in pars distalis are basophilic?

A

FSH (5%)
LH (10%)
TSH (10%)
ACTH (15-20%)

40
Q

What are the glycoprotein hormones?

A

TSH, FSH, LH

41
Q

What is the structure of the glycoprotein hormones?

A

dimer, with alpha and beta subunits

alpha subunit is similar among glycoproteins

beta subunits are fairly similar enough to have overlap, but different enough to have 3 different biological activities

42
Q

What main biological activity will the following recombined pair have:

alpha = TSH
beta = LH
A

LH

43
Q

What main biological activity will the following recombined pair have:

alpha = LH
beta = FSH
A

FSH

44
Q

How do assays measure the levels of glycoprotein hormones?

A

measure beta subunit

45
Q

What are the (plain) protein hormones?

A

GH, PRL

46
Q

How do protein hormones stain?

A

acidophilic

47
Q

What % of the pituitary is occupied by protein hormones?

A

75%

48
Q

What % of the pituitary is occupied by somatotrophic hormones?

A

~50%

49
Q

What % of the pituitary is occupied by lactotrophic hormones?

A

15-25%

50
Q

How are somatotrophic hormones affected by:

  • -T3?
  • -somatastatin?
  • -exogenous GH?
A
    • T3 = increases
  • -somatastatin = decreases
  • -exogenous GH = decreases
51
Q

How are lactotrophic hormones affected by pregnancy?

A

increased levels, and pituitary has increased blood flow

52
Q

What likely determines differentiation of precursor cell to lactotrophs or somatotrophs?

A

TH, prostaglandin, estrogen

53
Q

Target tissue(s) of ACTH?

A

z. lasciulata of adrenal cortex

54
Q

Target tissue(s) of TSH?

A

thyroid gland (particularly the cells lining the follicles)

55
Q

Major actions of ACTH?

A

increases adrenal growth
increases cortisol synthesis
increases cortisol secretion
increases plasma cortisol conc

(and indirectly, everything that cortisol does)

56
Q

Major actions of TSH?

A 
increases thyroid growth
increases TH synth and secretion
increases plasma TH conc
increased I trapping by thyr
increases thyr blood flow

(and indirectly, everything that T3 and T4 do)

57
Q

What variables increase release of ACTH?

A

increased CRH
increased stress
decreased cortisol
removal of adrenals

58
Q

What variables increase release of TSH?

A 
increased TRH
decreased T3
decreased T4
low I diet
removal of thyr
59
Q

What variables decrease release of ACTH?

A

decreased CRH
decreased stress
increased cortisol
synthetic glucocorticoids

60
Q

What variables decrease release of TSH?

A 
decreased TRH
increased T3
increased T4
increased somatostatins
exogenous THs
61
Q

What are the six releasing hormones, and what do they affect the release of?

A
  1. CRH = increased ACTH
  2. TRH = increased TSH
  3. GnRH = increased LH/FSH
  4. GHRH = increased GH
  5. Somatostatin = decreased GH
  6. Dopamine = blocks PL secretion
62
Q

T/F: Hormones must be lipid soluble in order to pass through the BBB and reach the hypothalamus.

A

F, the hypothalamus is OUTSIDE of the BBB

63
Q

How is anterior pituitary hormone secretion regulated?

A
  1. short loop feedback
    (secretion of a hormone from the ant pituitary acts on the hypothalamus via negative feedback)
  2. long loop feedback
    (hormone secreted from a peripheral endocrine gland acts on hypothalamus via negative or positive feedback)
64
Q

Why is it important to taper exogenous glucocorticoids?

A

cortisol acts via long feedback loop (or via negative feedback) to inhibit the hypothalamus from secreting CRH and ACTH

if GC are abruptly stopped, low levels of ACTH and CRH result in disrupted cortisol synthesis

65
Q

Target tissue(s) of PRL?

A 
females = mammary glands
males = testes, secondary sex tissues
66
Q

Target tissue(s) of GH?

A

most cells of the body (esp muscle, liver, cartilage growth plates in bones)

67
Q

Major actions of PRL?

A 
females = glandular tissue growth and milk synthesis
males = potentiate LH actions and testosterone actions
68
Q

What variables increase release of PRL?

A

decreased PIH (decreased DA)
increased TRH
suckling

69
Q

What variables increase release of GH?

A 
increased GHRH 
decreased somatostatin
deep sleep 
hypoglycemia
acute stress

(note 1st and 2nd occur simultaneously)

70
Q

What variables decrease release of PRL?

A 
increases PIH (increases DA)
decreases TRH
71
Q

What variables decrease release of GH?

A

decreased GHRH
increased somatostatin
sleeplessness

72
Q

How may estrogen affect prolactin secretion?

A

may interfere with dopamine’s inhibitory action

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