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DEMS Unit 4 > Hypothalamic Control of the Pituitary Gland > Flashcards

Hypothalamic Control of the Pituitary Gland Flashcards

1
Q

hypothalamic hormones are typically what type

A

peptides, except for dopamine, which is a catecholamine

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2
Q

how do hypothalamic hormones get to anterior pituitary

A

hypothalamo-hypophyseal portal system

  • blood enters median eminence through superior hypophyseal arteries and form capillary plexus
  • nerve terminals of hypothalamic neurons terminate here where neurohormones are released into capillary bed and transported via portal system to second cap plexus in anterior lobe
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3
Q

hypothalamic hormones

A

Thyrotropin releasing hormone, gonadotropin releasing hormone, growth hormone releasing hormone, somatostatin, prolactin inhibiting factor (DA)

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4
Q

action of thyrotropin releasing hormone (TRH)

A

increase TSH/PRL release from AP

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5
Q

action of GnRH

A

increased LH/FSH release from AP

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6
Q

Corticotropin releasing hormone action

A

increase POMC and ACTH release from AP

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7
Q

growth hormone releasing factor action

A

increased GH release from AP

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8
Q

action of somatostatin (GH inhibiting hormone)

A

decrease GH/TSH release from AP

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9
Q

Prolactin inhibiting factor action

A

decrease PRL from AP

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10
Q

how are hypothalamic hormones secreted from posterior pituitary

A

appropriate stimulation of neuron results in action potential generation –> Ca enters nerve terminal through VDCC causing liberation of hormone from secretory vesicles

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11
Q

what kinds of receptors do the hypothalamic hormones act on

A

G proteins

  • CRH and GHRH are coupled to Gs
  • Somatostatin with Gi
  • PIH/DA– Gi
  • GnRH - Gq
  • Gq also with TRH lactotrophs/thyrotrophs
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12
Q

what contributes to release of hormones from anterior pituitary

A

release of hormones dependent on calcium, but several intracellular cascades implicated in various pituitary cells. Membrane conductances also appear to play a role. The intracellular cascades also probably involved in regulating synthesis of various pituitary hormones.

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13
Q

Pituitary gland

A

endocrine control center responding to neural signals and catering to needs of various target tissues (e.g. thyroid, gonads, adrenal gland, bone), coordinating and regulating their functions
- connected to hypothalamus via pituitary stalk

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14
Q

major divisions of pituitary

A

anterior (adenohypophysis) and posterior (neurohypophysis)

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15
Q

from what is anterior pituitary derived

A

Rathke’s pouch (pharyngeal epithelium)

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16
Q

from what is posterior pituitary derived

A

neural tissue arising from an embryological evagination of diencephalon

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17
Q

what comprises the anterior pituitary

A

pars tuberalis, pars intermedia (intermediate lobe), and pars distalis (anterior lobe)

18
Q

from which part of adenohypophysis are hormones secreted

A

pars distalis/anterior lobe

19
Q

TRH

A

acts on cells called thyrotrophs to stimulate secretion of TSH and lactotrophs to release PRL via Gq

20
Q

GnSH

A

acts on gonadotrophs to stimulate secretion of luteinizing hormone (LG) and follicle stimulating hormone (FSH)

21
Q

GHRH

A

act on somatotrophs to stimulate secretion of growth hormone

22
Q

somatostatin

A

act on somatotrophs to inhibit GH secretion

23
Q

CRH

A

acts on corticotrophs to stimulate secretion of corticotropin (ACTH) and proopiomelanocortin (POMC)

24
Q

PIH

A

(prolactin inhibiting hormone) acts on lactotrophs to inhibit prolactin secretion

25
Q

Prolactin releasing factor

A

possibly also TRH; act on mammotrophs to stimulate secretion of prolactin

26
Q

polypeptide hormones from AP

A

PRL and GH

27
Q

glycoproteins from adenohypophysis

A

TSH, FSH, LH

- each comprised of identical alpha-subunit and unique beta subunit

28
Q

from what is ACTH derived

A

prohormone POMC, which is cleaved in both anterior and intermediate lobes of pituitary to give rise to ACTH, an N-terminal fragment and beta lipotropin

29
Q

what does cleavage of beta lipotropin produce

A

gamma-lipotropin adn beta-endorphin.

  • beta-endorphin contains sequence of metenkephalin
  • gamma-lipotropin contains sequence of beta-MSH
  • different in intermediate lobe, where alpha-MSH mostly generated after ACTH further cleaved
30
Q

parts of posterior pituitary

A

median eminence, infundibular stem, infundibular process (pars nervosa)

31
Q

where are hormones from posterior pituitary synthesized

A

in 2 nuclei in hypothalamus - supraoptic and paraventricular

32
Q

which peptides secreted by posterior pituitary

A

ADH and oxytocin

33
Q

neurons of hypothalammic nuclei extending into post pituitary

A 
magnocellular neurons (processes extend into posterior pituitary and end in pars nervosa)
- parvocellualr neurons -- end in median eminence close to endings of hypothalamic neurons producing anterior pituitary hormones -- aka post pituitary hormones can reach anterior lobe and have some function
34
Q

what neurons secrete ADH/oxytocin

A

magnocellular neurons from larger prohormone packaged into secretory vesicles and cleaved into the hormone + neurophysin protein as vesicles travel down axon

35
Q

ADH

A

antidiuretic hormone; secreted in response to increased plasma osmolarity or decreased blood pressure; acts on renal tubular cells and collecting ducts to alter water permeability adn conserve water.

36
Q

ADH receptors

A

V1–coupled to Gq and the phospholipase C pathway mediates vasopressive action of ADH

V2– coupled to Gs and cAMP pathway regulates effects of ADH on glomerular filtration rates in kidney

37
Q

when is oxytocin secreted

A

during passage of infant through cervix at childbirth, during sex, in response to suckling of infant during breast-feeding

  • acts on uterus around birth for myometrium contraction and contraction of myoepithelial cells in lactating women for milk ejection
38
Q

how often are pituitary hormones secreted

A

not constant but varied and pulsatile, with spikes in plasma levels. Can also have circadian rhythm (i.e. GH)

39
Q

most common way hormones are controlled

A

negative feedback by hormone itself or a metabolite

40
Q

2 places you can regulate hormone production

A
  • hormone production (can regulate timing and amplitude of pulsatile release over shorter term; also have circadian regulation over 24 hrs) itself
  • at the target: i.e. too much hormone, target cell can internalize receptors to prevent overstimulation (downregulation)
  • can also have full effect of some hormones even if some receptors taken away (spare receptors)
41
Q

function of hypothalamo-hypophyseal portal system

A

allows tiny amounts of hormone to be carried with minimal dilution to anterior pituitary

DEMS Unit 4 (16 decks)

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