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Urinary - Physiology > Regulation of Osmolarity > Flashcards

Regulation of Osmolarity Flashcards

1
Q

another name for ADH

A

vasopressin

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2
Q

site of vasopressin synthesis

A

supraoptic and paraventricular nuclei of hypothalamus, secreted from posterior pituitary

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3
Q

where is vasopressin stored

A

in the posterior pituitary

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4
Q

what does ADH stand for

A

anti-diuretic hormone

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5
Q

what receptors of the anterior hypothalamus mediate ADH secretion

A

osmoreceptors

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6
Q

what stimuli trigger ADH release

A

high osmolarity of plasma and low BP detected by atrial receptors

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7
Q

process of osmoreceptor reacting to osmolarity changes

A

high plasma osmolarity –> H2O out of cell –> cell shrinks –> stretch sensitive ion channel activated –> ADH secretion stimulated

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8
Q

true/false ADH regulation of osmolarity is rapid and precise

A

true - it has a half life of only 10 minutes so must act fast. only 2.5% increase of osmolality will produce a 10x increase in ADH secretion

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9
Q

ingestion of hypertonic solutions has what effect

A

increased solute to be excreted –> increased H2O excreted –> dehydration

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10
Q

in what part of the nephron does ADH has its effect on water regulation

A

collecting duct

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11
Q

what does ADH do to the collecting duct to increase water resorption

A

increases permeability of collecting duct cells to H2O

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12
Q

mechanism of ADH on collecting duct cell

A

ADH binds to cell –> cAMP messenger –> cell inserts AQP2 water pores into duct side membrane –> water absorbed through pores by osmosis into blood

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13
Q

H2O channels in membrane

A

aquaporins

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14
Q

when maximum ADH is secreted what happens to the osmolality of the collecting duct

A

H2O is very permeable and so when passing through the medulalry interstitium the collecting duct becomes equilibrated it.

The collecting duct is very concentrated at the tip of the medulla

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15
Q

where does water removed from collecting duct in medulla go

A

reabsorbed into vasa recta by it oncotic pressure

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16
Q

oncotic pressure of medullary vasa recta is higher/lower than normal (300)

A

higher - it has lost water to the interstitial gradient

17
Q

when ADH is absent what happens to the concentration of excreted urine

A

it is very low and dilute, lots of water because the ADH hasn’t been there making the collecting duct permeable to H2O

18
Q

urea is permeable/impermeabe to collecting duct cell membranes

A

permeable

19
Q

where is urea most permeable along the collecting duct

A

at the medullary tips

20
Q

what is antidiuresis

A

a state of dehydration and trying to reabsorb water at kidneys?

21
Q

effect of ADH on urea permeability

A

increases it

22
Q

what is the effect of urea being reabsorbed into the interstitium

A

reinforces the interstitial gradient around ascending loop of henle to maintain osmotic force moving across water through the pores made via ADH

23
Q

effect of ECF volume on ADH secretion

A

high ECF volume reduces ADH levels

24
Q

low pressure receptors

A

monitor return of blood in left and right atria

25
Q

high pressure receptors

A

carotid and aortic arch baroreceptors

26
Q

what receptors will respond first to ECF volume decrease

A

atrial receptors (low pressure)

27
Q

atrial receptor response to low ECF volume

A

low ECF volume –> low atrial receptor activity –> reduced inhibition of ADH via vagus –> ADH release

28
Q

what cardiovascular trigger will create a carotid and aortic receptor response

A

change in mean blood pressure

29
Q

through which nerve do the atrial receptors inhibit ADH release

A

the vagus nerve

30
Q

if someone is stressed, exercising or in pain, will ADH secretion go up or down

A

up

31
Q

ADH is suppressed by what drink

A

alcohol

32
Q

3 key controls of ADH release

A
  1. high plamsa osmolarity detected by hypothalamic osmoreceptors
  2. low blood volume detected by atrial stretch receptors
  3. decreased blood pressure detected by carotid and aortic baroreceptors
33
Q

what is diabetes insipidus

A

an ADH deficiency

34
Q

what is the urine like in diabetes insipidus

A

very dilute, no ADH doing water reabsorption

35
Q

why does someone with diabetes insipidus need to drink lots

A

because they are not reabsorbing H2O from urine so plasma osmolarity is low. this stimulates thirst

36
Q

name for diabetes insipidus where collecting duct is insensitive to ADH

A

peripheral DI

37
Q

name for diabetes insipidus where hypothalamic region is malfunctioning and ADH is not produced

A

central DI

38
Q

which type of diabetes insipidus is usually secondary to hypercalcaemia or hypokalaemia

A

peripheral (imbalance of these ions affects sensitivity to ADH)

39
Q

name of the collecting duct ADH receptors

A

V2

Urinary - Physiology (10 decks)

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