Volume regulation

Question 1

What is osmoregulation?

Answer 1

Regulation of the amount of water in the body to maintain constant ECF osmolality

Question 2

What is volume regulation?

Answer 2

• The regulation of blood volume and pressure to ensure effective circulating volume
• Accomplished by regulating total AMOUNT (not concentration) of sodium in the ECF

Question 3

What determines the ECF volume?

Answer 3

Total amount of sodium in ECF

Question 4

How is ECF volume sensed?

Answer 4

Atrial stretch receptors
Arterial baroreceptors

Question 5

What is RAAS

Answer 5

Renin-angiotensin-aldosterone system

Question 6

What is RAAS activated by?

Answer 6

Reduced renal prefusion
Increased sympathetic activity

Question 7

Why do these factors activate RAAS?

Answer 7

Both are interpreted as a fall in blood volume

Question 8

What does angiotensin II secretion do?

Answer 8

Increase aldosterone secretion
Causes vasoconstriction

Question 9

What increases aldosterone secretion?

Answer 9

RAAS
Increased plasma (K+)

Question 10

Effects of aldosterone on principal cells lining collecting duct

Answer 10

• Increases Na/K ATPase
• Increases expression of ENaC channels on luminal membrane

Resulting in

• Increased Na+ reabsorption
• Increased K+ secretion

Question 11

Effects of aldosterone on intercalculated cells of CD

Answer 11

• Increases H+ ATPase Resulting in
• Increased H+ secretion
• Increased HCO3- reabsorption

Question 12

What is liddles syndrome

Answer 12

Rare, genetic gain-of-function mutation in epithelial sodium channel (ENaC)

so more sodium retention so increased ECVF
Increased bp
Low renin
low aldosterone

Question 13

what is conns syndrome

Answer 13

• Primary hyperaldosteronism
• Often due to adenoma of adrenal cortex
• ↑ renal Na retention
• ↑ECVF
• ↑ BP
• ↓ plasma [K]
• Low renin - Renin is low because the normal control is by-passed. It’s the over-activity of the adrenal cortex producing the excess aldosterone.
• High aldosterone