6. K+-balance disorders

Question 1

Give the concentrations of K⁺ in the body

Answer 1

IC space = 150mmol/l

EC space = 5mmol/l

Question 2

Give the physiological importance of K⁺ in the body

Answer 2

Important for:

• Na⁺/K⁺ pump
• K⁺/H⁺ pump

Question 3

Give the effect of K⁺ on muscular irritability

Answer 3

Similar to that of Na⁺:

It tends to antagonise the effect of Ca²⁺

Question 4

List the disorders of K⁺ balance in the body

Answer 4

• Hypokalaemia
• Hyperkalaemia

Question 5

Give the blood concentration of hypokalaemia

Answer 5

<2.5mmol/l

Question 6

Give the causes of hypokalaemia

Answer 6

• Vomiting
• Abomasal displacement
• Diarrhoea
• Alkalosis
• Renal excretion (diuretics)
• Hyperaldosteronism
• Decreased K⁺ intake (rare)
• Insulin

Question 7

Hyperaldosteronism as a cause of hypokalaemia

Answer 7

Conn’s disease

Aldosterone:

• Na⁺ → In
• K⁺ → Out

Question 8

Insulin as a cause of hypokalaemia

Answer 8

• Insulin has an effect on the uptake of glucose to the cells via glucose/K⁺ cotransport system →
• Transfer of K⁺ inside the cells → EC hypokalemia

Question 9

Give the consequences of hypokalemia

Answer 9

• Muscles weakness
• Arrhythmias
• Partial hypokaluria
• Glucose intolerance
• Polyuria
• Polydipsia
• Na⁺ retention
• Alkalosis

Question 10

Muscle weakness as a consequence of hypokalaemia

Answer 10

Decreased neuromuscular irritability

Question 11

Arrhythmias as a consequence of hypokalaemia

Answer 11

Decreased conductance of stimuli

Question 12

Partial hypokluria as a consequence of hypokalaemia

Answer 12

Compensation of K⁺ loss to the EC space

Question 13

Glucose intolerance as a consequence of hypokalaemia

Answer 13

Insulin makes cells take up K⁺ as co-transport with glucose

Question 14

Give the causes of hyperkalaemia

Answer 14

• Acidosis
• Decreased renal excretion
• Cellular injuries
• Increase in intake
• Hypoaldosteronism
• Iatrogenic (medical) injections

Question 15

Acidosis as a cause of hyperkalaemia

Answer 15

1. Acidosis = High EC H⁺​ conc.
2. Uptake of H⁺ to the cells via K⁺/H⁺ pump
3. Increase of EC K⁺ levels

Question 16

Decreased renal excretion as a cause of hyperkalaemia

Answer 16

• H⁺ → Out
• In → K⁺

Question 17

Intake of … can cause hyperkalaemia

Answer 17

• Fertilisers
• Fresh Grass

Question 18

Hypoaldosteronism as a cause of hyperkalaemia

Answer 18

Addison’s disease

Question 19

List the consequences of hyperkalaemia

Answer 19

• Altered cardiac conduction
• Dilation of the heart in diastole
• Hyperkaluria

Question 20

Draw the figure giving the determining factors of K⁺ metabolism

Answer 20