Renal regulation of Potassium

Question 1

What is the effect of hyper and hypokalaemia on cell depolarisation?

Answer 1

Hyperkalaemia initially makes cells more excitable But also slows repolarisation of the cell if resting potential is greater than threshold potential
Hypokalaemia makes the resting potential more negative so it is harder to reach the threshold.

Question 2

How is potassium absorbed into the body?

Answer 2

From dietary intake there is passive diffusion of K across the small intestine and active transport in the colon (responsive to aldosterone)
Potassium can also come from cellular breakdown (haemolysis and tissue damage)

Question 3

How is internal K balanced?

Answer 3

Internal balance of K+ is maintained by the translocation of K+ between the ECF & ICF

Question 4

What hormones increase uptake into ICF (of muscle and liver)?

Answer 4

Insulin & adrenaline

Question 5

What causes release of K+ from cells?

Answer 5

Insulin or adrenaline deficiency
B- adrenergic receptor inhibition
Cell lysis
Exercise
Increased ECF osmolarity

Question 6

Where does K move in acidosis?

Answer 6

Potassium moves from ICF to ECF

Question 7

Where does K move in alkalosis?

Answer 7

Potassium moves from ECF to ICF

Question 8

Where does K move after a meal?

Answer 8

After a meal there is increase in K+ so insulin tells potassium to move into the cells because insulin is an agonist for Na/K ATPase

Question 9

High sodium leads to an ……………. in potassium excretion

Answer 9

Increase

Question 10

How does aldosterone cause an increase in Na/K ATPase channels?

Answer 10

Diffuses across membrane in distal tubule (principal cells) and binds to cytoplasmic receptors…hormone-receptor complex induces synthesis of proteins for the apical Na+ channel and Na+,K+ATPase

Question 11

Increases in aldosterone are mostly due to…

Answer 11

Most or all increases in aldosterone secretion may be attributable to increased activity of the RAAS and/or increased plasma level of K+.