HUF1-54 Regulation of K+ balance

Hypokalemia can result from:

• metabolic acidosis

• diarrhoea

• adrenal insufficiency

• hypovolemia

• hyperosmotic extracellular fluid

Increasing the extracellular potassium concentration will:

• increase the threshold for eliciting an action potential

• hyperpolarize the membrane potential

• increase extracellular hydrogen ion concentration

• decrease extracellular sodium concentration

• none of the above

Periodic hyperkalemic paralysis is characterized by high K+ concentration and muscle weakness. Which of the following is likely to cause muscle weakness?

• Hyperpolarization of the muscle cell membrane

• Inactivation of Na+ channels in the muscle cells

• Increased release of neurotransmitters from alpha motor neuron

• Decreased K+ concentration in the muscle cells

• Decreased ATP content in the muscle cells

The extracellular potassium concentration of a hyperkalemic patient can be decreased by administering:

• atropine

• adrenaline

• glucagon

• lactic acid

• isotonic saline

Renal correction of hyperkalemia will result in:

• alkalosis

• acidosis

• increased secretion of HCO3-

• increased secretion of H+

• increased excretion of Na+

The kidneys maintain K+ homeostasis by

• controlling K+ reabsorption at CCT

• controlling K+ secretion at CCT

• controlling K+ reabsorption at proximal tubule

• controlling K+ secretion at proximal tubule

• controlling Na+ secretion at proximal tubule

Which of the following on factors that affect K+ secretion is correct?

• Increased lumen‐negative transepithelial potential resulted from an increase in Na+ reabsorption would increase K+ secretion.

• High luminal flow decreases K+ secretion as the K+ are washed away quickly.

• Increased H+ pump activity at intercalated cells of the collecting tubule would increase K+ secretion.

• In diabetes mellitus, the insulin deficiency boosts the uptake of K+ by cells, reducing K+ secretion.

• β₂ and α adrenergic agonists inhibit release of insulin from pancreatic β cells, leading to hyperkalemia.

Describe how a decreased distal flow rate affects the net secretion of K+.