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Year 2- Urinary > Regulation of Osmolality > Flashcards

Regulation of Osmolality Flashcards

1
Q

What hormone controls water regulation?

A

ADH aka anti-diuretic hormone

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2
Q

Where is ADH
-synthesised?
-stored?

A

Synthesised in the hypothalamus
Stored and released from posterior pituitary

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3
Q

What is the half-life of ADH?

A

10 minutes

->this means it can be rapidly adjusted depending on the body’s need for water

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4
Q

What primarily controls ADH secretion?

A

Plasma osmolarity

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5
Q

How does plasma osmolality determine the secretion of ADH?

A

When the osmotic pressure of plasma increased, the release of ADH-secreting hormones from the hypothalamus is increased, which in turns increased release of ADH from the posterior pituitary

->kind of like a negative feedback loop we learned about in endocrine. wordy but read through and understand cos rn I cba xx

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6
Q

What are changes in the neuronal discharge of ADH secreting hormones mediated by?

A

Osmoreceptors in the anterior hypothalamus

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7
Q

What are osmoreceptors?

A

Cells which can change their cellular volume in response to osmotic changes

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8
Q

What happens to osmoreceptors if osmolality increases?

A

Increased water out of cell so cells shrink

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9
Q

What happens to the release of ADH-secreting hormones and ADH when there is high osmolality?

A

Increased neuronal discharge meaning increased ADH secretion

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10
Q

What happens to osmoreceptors if osmolality decreases?

A

Water enters cell
Cells swell

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11
Q

What happens to the release of ADH-secreting hormones and ADH when there is low osmolality?

A

Decreased neuronal discharge meaning decreased ADH secretion

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12
Q

Therefore, what effect does the change in volume of osmoreceptors have?

A

Leads to changes in osmoreceptor discharge

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13
Q

What is the normal osmolality of plasma?

A

280-190mOsmoles/Kg water

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14
Q

If osmolality increases due to an increase in NaCl, what happens?

A

Decreased volume of osmoreceptor
Increased discharge and ADH release

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15
Q

If osmolality increases due to an increase in urea, what happens?

A

No change in volume, discharge or ADH release

->this is because urea is an ineffective osmole idk gal these slides confuse me

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16
Q

What is the amount of urine produced dependant on?

A

ADH
Amount of solute to be excreted

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17
Q

Okayyyyy so lets say there was 2400mOsmoles of solute to be excreted, how much urine would be produced?

A

2 litres

-> maximum urine concentration is 1200-1400mOsmol/L hence why two litres will be produced

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18
Q

Ingestion of hypertonic solutions, like seawater, can cause death. Why?

A

Increases solute load to be excreted meaning increased urine flow, leading to dehydration and potentially death

->okay just for interest but if you were stuck in the middle of the sea, drinking seawater would actually quicken death!

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19
Q

By addition of aquaporins into the luminal membrane, what effect does this have on permeability of the collecting ducts?

A

Increases the permeability towards water of the collecting ducts

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20
Q

If ADH is present, how does this effect the permeability of the collecting duct?

A

ADH increases the permeability for water

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21
Q

What amount/concentration of urine does the presence of ADH produce?

A

Smaller volume of highly concentrated urine

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22
Q

In the absence of ADH, what happens to the collecting duct’s permeability to water?

A

Collecting ducts become impermeable to water in absence of ADH

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23
Q

What happens to urine concentration/amount in the absence of ADH?

A

Larger volume of more dilute urine compensating for water excess as cannot be removed without ADH

24
Q

So…. what happens to urine if there is excess water?

A

Want to get rid of water so more dilute, higher quantity of urine

25
Q

So…. what happens to urine if there is water deficit?

A

Water wants to be conserved so higher concentration but less quantity of urine

26
Q

How is urea concentration effected by the presence of ADH?

A

Presence of ADH means there is movement of water out of the collecting ducts, this greatly concentrates urea remaining in the ducts

27
Q

In an anti-diuretic situation with high levels of ADH, what happens to urea?

A

Reabsorbed from the collecting duct into the interstitium where it reinforces the interstitial gradient in the loops of Henle

28
Q

Why is it important that the urea is reabsorbed from the tubule?

A

If it remained in the tubule, it would exert osmotic effects to hold water in the tubule and reduce potential for rehydration

29
Q

As well as osmolarity being a trigger for ADH release, what else has an effect?

A

ECF volume

30
Q

If there is increased ECF volume, what happens to the ADH secretion?

A

Decreased ADH secretion

31
Q

If there is decreased ECF volume, what happens to the ADH secretion?

A

Increased ADH secretion

32
Q

By decreasing ADH, does this promote diuresis or anti-diuresis?

A

Diuresis

->and vice versa

33
Q

Control of ADH secretion is linked to the rate of discharge of the stretch receptors in low and high pressures of the circulation.
Where would you find low pressure receptors?

A

Left and right atria
Great veins

34
Q

Control of ADH secretion is linked to the rate of discharge of the stretch receptors in low and high pressures of the circulation.
What are the high pressure receptors?

A

Carotid and aortic arch baroreceptors

35
Q

Low pressure receptors are sometimes known as volume receptors, why is this?

A

They monitor the return of blood to the heart and the ‘fullness’ of the circulation

36
Q

Which receptors are mostly affected by a moderate decrease in ECG volume?

A

Atrial receptors

37
Q

What is the subsequent effect of decreased ECF volume on receptor discharge and ADH release?

A

Decreased ECF -> Decreased Atrial receptor discharge -> Increased ADH release

38
Q

List some stimuli which can increase release of ADH.

A

Pain, emotion, stress, exercise, smoking, morphine.

39
Q

List some stimuli which can decrease release of ADH.

A

Alcohol

40
Q

What causes diabetes insipidus?

A

ADH deficiency

41
Q

What happens if we don’t have ADH?

A

Go into a massive diuresis situation

42
Q

Gal, what is diuresis?

A

Increased or excessive production of urine

43
Q

Peripheral diabetes inspipius?

A

When the collecting duct is insensitive to ADH

44
Q

Central diabetes insipidus?

A

Hypothalamus areas synthesising ADH may become damaged or diseased

45
Q

What can cause damage to the hypothalamic areas synthesising ADH, in turn causing central diabetes insipidus?

A

Tumours
Meningitis

46
Q

What are the characteristics of diabetes insipidus?

A

Passing of very large volumes or dilute urine, often >10L / day
Polydipsia

47
Q

How can central diabetes insipidus be treated?

A

Giving ADH

48
Q

Why can’t ADH be given to treat peripheral diabetes insipidus?

A

Thirst mechanism required for survival

->idk

49
Q

What is the average urine output for a day?

A

1.5L

50
Q

What is the osmolality of final urine?

A

50-1200mOsm

51
Q

In the loop of Henle, how much fluid passes through the Bowman’s capsule each day?

A

180L

52
Q

In the loop of Henle, how much fluid passes through the end of the proximal tubule each day?

A

54L

53
Q

In the loop of Henle, how much fluid passes through the end of the loop each day?

A

18L

54
Q

What is the osmolarity of the fluid in the Bowman’s capsule?

A

300mOsmoles

55
Q

What is the osmolarity of the fluid in the end of the proximal tubule?

A

300 mOsmoles

56
Q

What is the osmolarity of the fluid in the end of the loop of Henle?

A

100 mOsmoles

57
Q
A

Year 2- Urinary (22 decks)

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