Renal Physiology 3 (Renal)

Question 1

What causes ADH to be released?

Answer 1

Essentially, increased plasma osmolarity (increased [Na+]).

Increased ECF osmolarity = osmoreceptor cells shrink.
Shrink = release of ADH to act on DCT/CT/CDs to open aquaporins.

Reabsorption of water is increased.

Question 2

What is the mechanism of action of ADH?

Answer 2

ADH increases aquaporin activity.

ADH translocated ACQ-2 to luminal membrane to allow H2O diffusion in DCT/CT/CD

AQP3 and AQP4 are always open on basement membrane.

This means only one side of the membrane is waterproofed.

Question 3

Describe the renin-aldosterone-angiotensin system

Answer 3

Decrease in renal perfusion (juxtaglomerular apparatus) causes renin to be released.

Renin causes release of AT1
AT1 is converted to AT2 by ACE

AT2 increases Na+ reabsorption and K+ excretion, and causes arteriole vasoconstriction. AT2 causes aldosterone secretion, which also increases Na+ reabsorption and K+ excretion.

This results in increased water and salt retention, leading to increased perfusion of JGA.

Question 4

What does ANP do?

What causes its release?

Answer 4

Opposes anything that aldosteron/angiotensin II does.

Decreases H2O and Na+ reabsorption.

Increased BP/blood volume causes distension of cells in cardiac artia, releasing ANP.
ANP inihibts Na+ reabsorption.

Question 5

Where is potassium stored in the body?

What factors shift potassium into cells, and what releases it?

Answer 5

98% is stored in ICF, sequestered inside cells.

Insulin and adrenaline, alkalosis shifts potassium INTO cells.

Cell lysis and muscle damage kills cells, releasing into ECF. Acidosis shifts K from cells into ECF

Question 6

Where is potassium secretion and resorption regulated?

Answer 6

In principal cells in the late DCT/CT

Question 7

Describe K+ feedback control

Answer 7

Increased ECF [K+] stimulates Na+/K+ ATPase and stimulates aldosterone secretion.

Results in secretion of K+.

Question 8

What is the proper name for the ‘thirst centre’ in the brain?

Answer 8

Hypothalmic antroventral-3rds-ventricle (AV3V) region.

Question 9

What conditions increase and decrease thirst?

Answer 9

Increase thirst: Increased osmolarity, decreased blood volume and pressure, increased angiotensin.

Decreased thirst is caused by the opposites.

Question 10

What is the control centre for appetite for salt?

What are the two primary stimulants for increased salt appetite?

Answer 10

Antroventral-3rd-ventricle - same as thirst.

Decreased ECF [Na]
Decreased BP/volume