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Renal Physiology > Regulation of Osmolarity > Flashcards

Regulation of Osmolarity Flashcards

1
Q

What is water regulation controlled by?

A

ADH (Vasopressin)

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2
Q

What is ADH?

A

A polypeptide hormone

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3
Q

Where is ADH synthesised?

A

Supraoptic paraventricular nuclei of the hypothalamus

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4
Q

What part of the piuitary does ADH come from?

A

Posterior

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5
Q

What controls ADH secretion?

A

Plasma osmolarity

ECF volume

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6
Q

What do changes in volume of osmoreceptors result in?

A

Changes in osmoreceptor discharge (stretch sensitive ion channels)

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7
Q

What is the normal plasma osmolality?

A

280 - 290 mOsm/kg

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8
Q

What would an increase in osmolarity lead to?

A

H20 out of the cell
Cell shrinks/ sensitive ion channel activated
Increased neural discharge
Increased ADH secretion

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9
Q

What does a decreased osmolarity lead to?

A

H20 enters the cells
Cells swell
Decreased neural discharge
Decreased ADH secretion

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10
Q

What do the osmoreceptors detect?

A

Tonicity - not the osmolarity

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11
Q

What is tonicity?

A

Penetrating solutes concentration (e.g. glucose, urea)

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12
Q

Do solutes that penetrate membranes and move together with water produce any tonicity?

A

No

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13
Q

Where is the site of water regulation?

A

The collecting duct

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14
Q

What is the permeability of the collecting duct controlled by?

A

ADH

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15
Q

What does ADH stand for?

A

Anti diuretic hormone

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16
Q

How does ADH alter the permeability of the collecting duct?

A

Changes the amount of aquaporins (which allow water to pass through)

17
Q

What happens if high ADH present?

A

H20 is able to leave the collecting duct

18
Q

What happens if maximum ADH is presen?

A

Becomes highly concentrated at the tip of the medulla - produces a small volume of highly concentrated urine

19
Q

How is H20 reabsorbed?

A

By the oncotic pressure of the vasa recta

20
Q

Urea in the prescence of ADH

A

Movement of H20 out of the collecting ducts greatly concentrates the urea remaining in the ducts
Collecting duct membranes are relatively permeable to urea, particuarly towards medullary tips/
So as urea approaches these, there is an increasing tendency for these to move out down its concentration gradient - so it is reabsorbed

21
Q

What does an increased ECF volume do to the ADH conc?

A

Decreases ADH

22
Q

What does a decreased ECF volume do to the ADH conc?

A

Increases ADH

23
Q

Where are low pressure receptors located?

A

Left and right atria

Great veins

24
Q

What do low pressure receptors monitor?

A

The return of blood to the heart

The “fullness” of the circulation

25
Q

Where are the high pressure receptors located?

A

Carotid and aortic arch baroreceptors

26
Q

What do moderate decreases in ECF volume primarily affect?

A

The atrial receptors

Renal Physiology (7 decks)

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