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Year 2 Urinary (JK) > Regulation of osmolarity > Flashcards

Regulation of osmolarity Flashcards

1
Q

What is water regulation controlled by? Give some other names for this

A

ADH/vasopressin/arginine vasopressin

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2
Q

Where is ADH synthesises?

A

supraoptic and paraventricular nuclei of the hypothalamus in the brain

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3
Q

Where is ADH released from?

A

posterior pituitary

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4
Q

Primary control of ADH secretion

A

plasma osmolarity

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5
Q

Describe how an increase in plasma osmolarity leads to an increase in ADH secretion?

A

increase oncotic pressure
rate of discharge of ADH secreting neurons increased
ADH release increased

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6
Q

How is the change in neuronal discharge of ADH mediated?

A

osmoreceptors

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7
Q

Where are osmoreceptors found?

A

anterior hypothalamus close to the SO and PVN

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8
Q

Is a high osmolarity high or low water concentration?

A

low

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9
Q

Explain what happens to an osmoreceptor if osmolarity increases

A

water moves out of cell and shrinks

activate stretch sensitive ion channels which increases neuronal discharge and ADH secretion

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10
Q

What kind of system is the ADH - plasma osmolarity system described as?

A

high gain

sensitive

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11
Q

What must occur to cause an increase in ADH? (not just increase osmolarity)

A

increased TONICITY

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12
Q

What is tonicity?

A

non penetrating particles which cause a movement of water

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13
Q

Why do some solutes not exhibit tonicity?

A

solutes that can penetrate membranes move together with water and do not create an osmotic drag/tonicity

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14
Q

Is urea or NaCl an ineffective osmole?

A

urea

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15
Q

What 2 things is the amount of urine produced dependent on?

A

ADH

amount of solute to be excreted

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16
Q

Why do hypertonic solutions eg seawater cause dehydration?

A

increase solute load to be excreted, increase urine flow and hence more water required to be excreted with solute than was ingested

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17
Q

How does ADH increase permeability of the collecting duct?

A

bind to membrane receptor
activate cAMP
increase aquaporin uptake into apical membrane
water absorbed by osmosis into the blood

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18
Q

What happens to water leaving the duct if ADH is max?

A

equilibrate with medullary interstitium and is highly concentrated at tip of medulla

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19
Q

type of urine produced when ADH is max

A

small, highly concentrated

20
Q

What happens to the water when max ADH is present?

A

reabsorbed by vasa recta as oncotic pressure is high

21
Q

What happens when ADH Is absent? Why? Type of urine

A

CD impermeable to water
medullary gradient is ineffective
high amount, dilute urine

22
Q

What can concentration fall to when ADH absent?

A

30-50

23
Q

What does urea play an important role in?

A

production of highly concentrated urine

24
Q

What happens to urea in collecting duct if ADH is present?

A

greatly concentrates due to water out of CD

25
Q

Is the CD permeable or impermeable to urea? Where especially?

A

permeable

medullary tips

26
Q

What happens when urea reaches medullary tips?

A

moves out of CD - enhanced by ADH

27
Q

What happens when urea leaves collecting duct when ADH present?

A

reabsorbed into interstitium
reinforce interstitial gradient at ascending loops of henle
saves water and uraemia (vasa recta)

28
Q

Why is it important for urea to be reabsorbed by vasa recta?

A

if it remained in tubule would exert osmotic effect and hold onto water into tubule making rehydration difficult

29
Q

Is urea retention or water conservation more important?

A

water

30
Q

What is the 2nd thing which effects ADH secretion?

A

ECF volume

31
Q

What happens to ADH secretion as ECF volume increases and decreases

A

decreases, ADH increases

32
Q

Where are low pressure receptors found?

A

left and right atria and great veins

33
Q

What do the low pressure receptors monitor?

A

volume - Venous return to the heart and hence fullness of CVS

34
Q

Where are the high pressure receptors found?

A

carotid and aortic arch baroreceptors

35
Q

What receptors are affected most by a moderate decrease in ECF volume?

A

atrial receptors

36
Q

What is the relationship between the rate of ADH secretion and discharge of stretch in high and low pressure receptors?

A

inverse

37
Q

When will high pressure receptors contribute to changes in ADH secretion?

A

when MBP affected

38
Q

What kind of cells are ADH secreting cells?

A

neurons

39
Q

Importance of ADH secreting cells being neurones

A

integrate inputs

40
Q

What are some examples of things which increase ADH

A

pain, stress, emotion, nicotine, morphine, exercise

41
Q

What is an example of something which decreases ADH?

A

alcohol

42
Q

What is the cause of diabetes insipidus?

A

ADH deficiency

43
Q

Cause of central DI

A

hypothalamic areas secreting ADH affected eg tumour, meningitis, surgery

44
Q

Causes of peripheral DI

A

collecting duct insensitive to ADH

hypokalaemia, hyperkalaemia, genetic

45
Q

Symptoms of DI

A

large volumes of concentrated urine

polydipsia

46
Q

How is central DI treated?

A

ADH(AVP)

47
Q

How is peripheral DI treated?

A

usually due to hypokalaemia or hypercalcaemia so at this - will usually resolve
cannot give ADH due to thirst mechanism

Year 2 Urinary (JK) (26 decks)

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