06.2 Control of Potassium Flashcards
As the ECF [K+] increases what happens to the resting membrane potential of cells?
Increases (becomes less negative)
What are the two processes that regulate potassium concentration?
Internal balance - shifts K+ between ICF and ECF
External balance - renal secretion
By what transporter is potassium moved into cells?
NaKATPase
How is potassium removed from cells?
Potassium channels
What hormones increase the uptake of potassium into cells?
Insulin.
Aldosterone.
Catecholamines.
What acid base state increases the uptake of potassium into cells?
Alkalosis.
Name some factors that can cause potassium to leave cells.
Exercise.
Cell lysis.
Acidosis.
Increases ECF osmolarity.
What factors in a diabetic can cause them to become hyperkalaemic?
Decrease in insulin.
Decrease in pH.
Increase in plasma tonicity.
What acid base balance problems can hyperkalaemia and hypokalaemia cause?
Acidosis and alkalosis respectively.
As the ECF [K+] decreases what happens to the resting membrane potential of cells?
The resting membrane potential will drop and become hyperpolarised.
Where is the majority of potassium reabsorbed in the kidneys?
PCT
What cells secrete potassium in the kidneys?
Principle cells.
Where are principle cells located?
DCT + CD
How do principle cells secrete potassium?
NaKATPase on the basolateral membrane.
Na+ and K+ channels on the apical membrane.
What does an increase in ECF [K+] do to the tubule?
Stimulates NaKATPase on the basolateral membrane.
Stimulates aldosterone.
What does aldosterone do to potassium levels?
Causes them to decrease as aldosterone stimulates, NaKATPase and K+ and Na+ channels on principle cells.
How does an increased distal tubular flow rate impact potassium levels?
Increases potassium loss
What membranes can the change in potassium levels alter?
Cardiac conduction Cardiac pacemaker Neuronal function Skeletal muscle function Smooth muscle function
What can hyperkalaemia do to the heart?
Arrhythmia
Heart block
These can lead to a cardiac arrest
How can hyperkalaemia affect the GI system?
Paralytic ileus.
How can you treat hyperkalaemia?
Glucose + insulin.
Calcium gluconate to reduce the impact of potassium on the heart.
Remove excess potassium via dialysis.
Treat the cause - stop K+ sparing diuretics, treat diabetes etc.
What can cause hypokalaemia?
Diarrhoea/vomiting
Certain diuretics
Increased aldosterone
What are the cardiovascular features of hypokalaemia?
Arrhythmias
What are the GI features of hypokalaemia?
Paralytic ileus.
