ECF fluid regulation 2

Question 1

What promotes Na+ reabsorption and it’s excretion

Answer 1

Aldosterone = reabsorption atdistal tubule

Atrial Natriuretic Peptide (ANP) = excretion at distal tubule?

Question 2

Aldosterone’s effect on K+ and where

Answer 2

Excretion at distal tubule

Question 3

What is Conn’s syndrome

Answer 3

1° hyperaldosteronism due to a tumour of the adrenal cortex

Hypokalaemic but not hypernatraemic

Question 4

Why does one not become hypernatraemic in Conn’s syndrome

Answer 4

ANP release cause natriuresis (loss of water and NaCl in urine)

Question 5

Why does hyperglycaemia in DM lead to a coma

Answer 5

1. High [BG] exceeds the maximum reabsorptive capacity in the proximal tubule
2. Glucose remains in tubule, exerts an osmotic effect to retain water in the tubule.
3. [Na+] in the lumen is decreased because of the increased water.
4. Less water leaves descending limb due to glucose and excess Na+ exerting an osmotic effect to retain water in tubule.
5. The macula densa detects the high rate of NaCl delivery so renin secretion will be suppressed => Na+ reabsorption at distal tubule decreased.
6. A large volume of nearly isotonic urine will be excreted reducing Pulse Volume.

All resulting in inadequate blood flow to brain due to hypovolaemia

Question 6

Difference between hypo and hyperglycaemic comas

Answer 6

Hyper = inadequate blood flow to brain 
Hypo= inadequate glucose delivered to brain