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Urinary > Regulation of Osmolality > Flashcards

Regulation of Osmolality Flashcards

1
Q

What type of hormone is ADH?

A

Polypeptide

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2
Q

Where is ADH released from?

A

Posterior pituitary

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3
Q

How is ADH secretion controlled?

A

Primarily by plasma osmolarity

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4
Q

How are changes in neuronal discharge mediated?

A

Osmoreceptors in the anterior hypothalamus

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5
Q

What happens when the osmolarity increases?

A

More water leaves the cell > cell shrinks > stretch sensitive ion channel activated > increased neural discharge > increased ADH secretion

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6
Q

What happens when the osmolarity decreases?

A

Water enters the cell > cells swell > decreased neural discharge > decreased ADH

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7
Q

What happens when there is an increase in osmolarity but not in tonicity?

A

It is ineffective at causing an increase in ADH

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8
Q

What is tonicity?

A

The relative concentration of solutes dissolved in solution: determines the direction and extent of the diffusion

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9
Q

What effect does changing urea concentration have on ADH release?

A

No effect: urea is an ineffective osmole

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10
Q

What factors affect the amount of urine produced?

A

ADH conc. and the amount of solute to be excreted

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11
Q

What happens when hypertonic solutions e.g. sea water are ingested?

A

It increases the solute load, increasing urine flow and leading to dehydration

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12
Q

Where is the site of water regulation?

A

Collecting duct

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13
Q

What effect does ADH have on the permeability of the collecting ducts to water?

A

It increases the permeability of the collecting duct to water by incorporating H2O channels (aquaporins) into the luminal membrane

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14
Q

What happens to the urine at maximal ADH conc.

A

A small amount of highly concentrated urine which contains less filtered water than of solute

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15
Q

What happens when ADH is absent?

A

The collecting ducts are impermeable to water so that the medullary interstitial gradient is ineffective in inducing water movement out of the collecting duct. Large amount of diluted urine is produced

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16
Q

What happens to urea in the presence of ADH?

A

As the water moves out of the collecting ducts the urea becomes concentrated

17
Q

What happens to the late medullary collecting duct permeability to urea in presence of ADH?

A

It is greatly enhanced

18
Q

What happens to urea when the ADH is high?

A

The urea will be reabsorbed from the collecting duct into the interstitium where it reinforces the interstitial gradient

19
Q

Why is it important that urea is reabsorbed?

A

If it remained in the tubule it would exert an osmotic effect and hold the water in the tubule

20
Q

How does ECF volume affect the ADH secretion?

A

It is an inverse relationship between ADH secretion and the stretch receptors in the low and high pressure receptors

21
Q

Where are the low pressure receptors located?

A

L&R Atria and Great Veins

22
Q

What are the high pressure receptors?

A

Carotid and aortic arch baroreceptors

23
Q

Which receptors are primarily affected by moderate decreases?

A

Atrial receptors

24
Q

What happens if the ECF volume changes enough to affect the MBP?

A

The carotid and aortic receptors will contribute to the ADH secretion

25
Q

Is there an increase in ADH secretion when going from lying down to standing up?

A

Yes

26
Q

Which stimuli increase ADH secretion?

A

Pain, emotion, stress, exercise, nicotine, morphine and traumatic surgery

27
Q

Which stimulus decrease ADH secretion

A

Alcohol

28
Q

What is diabetes inspipidus?

A

ADH deficiency

29
Q

What is the clinical presentation of diabetes insipidus?

A

Polydipsia (increased drinking) and polyuria (increased urine volumes)

30
Q

How is central diabetes insipidus treated?

A

Giving ADH

31
Q

How is peripheral diabetes insipidus treated?

A

Cannot give ADH. Usually secondary to hypercalcaemia or hypokalaemia so treat the ion imbalance

Urinary (9 decks)

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