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Metabolic Endocrinology > Hypothalamus-posterior pituitary > Flashcards

Hypothalamus-posterior pituitary Flashcards

1
Q

what types of neurons are found in hypothalamus reaching posterior pituitary

A

magnicellular neurons

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2
Q

what is the particularity of the magnicellular neurons

A

they extend axons to posterior pituitary gland

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3
Q

which are the 2 hormones of the posterior pituitary

A

oxytocin and vasopressin

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4
Q

which magnicellular neurons release oxytocin

A

paraventricular nucleus PVN which contains both magnicellular and parvicellular neurons

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5
Q

which magnicellular neuron releases Vasopressin/ADH/AVP?

A

supraoptic nucleus SON (80-90% neurons produce AVP

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6
Q

ADH

A

antidiuretic hormone

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7
Q

AVP

A

arginine vasopressin

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8
Q

Oxytocin and AVP are made up of .. AA, making them …

A

9 AA - nanopeptides

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9
Q

in which chromosome are AVP and OXT genes found in humans

A

chromosome 20

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10
Q

what is the difference between OXT and AVP

A

their nucleotide sequence varies by 2 AA

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11
Q

what is the difference between LVP and AVP

A

LVP - lysine vasopressin found in pigs
AVP - arginine vasopressin in humans
=> both at position 8

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12
Q

structure of AVP and OXT

A

ring structure connection AA at position 1 and 6 due to di-sulfide bridges between 2 cysteine

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13
Q

when are the pro hormones of OXT and AVP cleaved?

A

as vesicles/granules traverse through the axons

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14
Q

storage of OXT and AVP is enough for ….. days

A

30-50 days

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15
Q

Function of ADH/AVP

A

regulation of water retention and thirst - primary regulator of blood osmolality
> water retention by kidney + contraction of blood vessels (arterioles)

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16
Q

function of oxytocin

A

contraction of smooth muscles cells - myoepithelial cells of the alveoli in lungs and smooth muscle cells of the uterus during labor

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17
Q

vasopressin/antidiuretic hormone are names derived from 2 physiologic systems regulated which are?

A
  1. osmotic

2. pressure/volume

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18
Q

what are the different receptors used by AVP/ADH

A

V1a/b and V2

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19
Q

where are V1a receptors found and what are their respective functions

A
  1. vascular smooth muscle - vasoconstriction, myocardial hypertrophy
  2. platelets - platelet aggregation
  3. hepatocytes - glycogenolysis
  4. myometrium - uterine contraction
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20
Q

where are V1b receptors found and what’s their function

A

anterior pituitary - ACTH release (regulates CRH signaling)

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21
Q

where are V2 receptors found and what are their respective functions?

A
  1. basolateral membrane collecting tubule - insertion of AQP2 water channels into apical membrane, induction of AQP2 synthesis
  2. vascular smooth muscle - vasodilation
22
Q

vasopressin receptor signaling via V2 receptor

A

Gs

cAMP - PKA: insertion of aquaporin 2 channels on plasma membrane thorough which water can pass through

23
Q

vasopressin receptor signaling via V1a and V1b receptors

A

V1a: vascular and uterine smooth muscle contraction or exocytosis
V1b: anterior pituitary - release of ACTH
GPCR - Gq - PLC - IP3 - increase in calcium concentration in cytoplasm

24
Q

how does the regulation of osmolality work?

A

involves osmostat in hypothalamus

  • sensation of osmotic pressure
  • osmoreceptors most sensitive to sodium - detect osmotic changes in blood
  • > end result: control/conservation of water
25
Q

osmolarity vs osmolality

A

number of solutes in 1L vs number of solutes in 1kg

26
Q

which hormones regulate blood pressure and blood volume?

A

vasopressin, renin-angiotensin system and aldosterone

27
Q

how to the osmoreceptors found in the hypothalamus detect osmotic changes in blood

A

via circumventricular organ OVLT

28
Q

what is the normal blood osmotic pressure?

A

280 to 295 mOsm/kg H2o

29
Q

what happens under hypotonic conditions

A

solute concentration inside the cell is lower than normal due to actual concentration or due to increased solvent volume

30
Q

what happens under hypertonic conditions

A

more souls present due to actual increase or decrease in volume itself

31
Q

mechanism for correction of low blood pressure by vasopressin

A

vasopressin from posterior pituitary acts on smooth muscle causing vasoconstriction + at kidney level, increase water retention by binding on receptors on distal tubule cells activating GPCR - cAMP pathway and insertion of aquaporins which increases blood volume
=> vascular constriction and increased blood volume => increased blood pressure

32
Q

what is thirst and what triggers it?

A

defense mechanism to replace water lost through urine, respiration, and perspiration
triggered by changes in osmolality/volume - usually hypovolemia [low blood volume] and decreased BP

33
Q

AVP is more sensitive to … than ….

A

osmolality than volume/pressure

34
Q

how is oxytocin release regulated?

A

regulated by suckling stimulus

35
Q

oxytocin regulates … of milk under the influence of ….

A

ejection of milk under the influence of prolactin

36
Q

oxytocin can be produced elsewhere than in pituitary, where?

A

ovaries (corpus luteum) - involved in luteolysis

and in uterus in some species

37
Q

how is lactation/milk ejection done

A

secretion of oxytocin stimulated by suckling or tactile stimuli - oxytocin receptors on myoepithelial cells causing contraction when binding

38
Q

other function of oxytocin

A

contraction of smooth muscle around uterus during parturition/birth - as pregnancy comes to an end, myometrium becomes sensitive to oxytocin as oxytocin receptor concentration increases

39
Q

how is the uterus maintained relaxed during pregnancy

A

by progesterone and relaxin

40
Q

uterine contraction by oxytocin co-occurs with ….

A

prostaglandin F2a

41
Q

mechanism of action of oxytocin

A
  • binds to GPCR - PLC - IP3 - cytoplasmic [calcium] increases - MLCK - smooth muscle contraction
42
Q

what can high levels of oxytocin be associated with?

A

with more socially positive behaviour - monogamy or help female raise the young ones

43
Q

what are the causes of diabetes insipidus

A
  • lack of vasopressin
  • lack of response to vasopressin in kidney
  • receptor defect or aquaporin defect
  • rapid metabolism of vasopressin
  • pregnancy [transient diabetes insipidus]
44
Q

what is diabetes insipidus

A

excretion of large volume of urine diabetes) that is hypotonic, dilute and tasteless (insipid)

45
Q

osmotic pressure and blood volume causing vascular constriction or dilation also requires …. sensitive to pressure change

A

baroreceptors located in arch or aorta in carotid arteries

46
Q

AVP is released after …. decrease in volume and …. decrease in pressure

A

8% and 5%

47
Q

what is vasoconstriction

A

increased contraction of circular smooth muscle in the arteriolar wall, which leads to increased resistance and decreased flow through the vessel

48
Q

what is vasodilation

A

decreased contraction of circular smooth muscle in the arteriolar wall which leads to decreased resistance and increased flow through the vessel

49
Q

what causes vasoconstriction

A
  • increased myogenic activity
  • increased oxygen
  • decreased CO2
  • increases sympathetic stimulation, VASOPRESSIN, angiotensin 2. cold
50
Q

what causes vasodilation

A
  • decreased myogenic activity
  • decreased oxygen
  • increase in CO2
  • decreased sympathetic stimulation, histamine release, heat

Metabolic Endocrinology (10 decks)

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