Control Of Potassium Flashcards
What is the immediate control of increased plasma K+, what channel mediates this?
What is the delayed control?
Internal balance
Translocation of K+ from the ECF to the ICF
Na K ATPase
External balance - renal excretion
Name 3 factors increasing K uptake into cells.
Hormones (insulin, aldosterone and catecholamines)
Alkalosis
Increased K+ in ECF
Give 5 factors that lead to increased K+ translocation out of cells.
Exercise Acidosis Cell lysis Increased ECF osmolarity Low ECF K+
Name 2 factors which offset K+ increase in the blood post-exercise.
Uptake of K+ by non contracting cells
Catecholamine release increases during exercise which contributes to increased K+ uptake by cells.
What is the time frame for external balance to occur around?
6-12 hours
Where is Potassium secreted into the tubule?
DCT and cortical collecting ducts (principal cells_
Where does the majority of K+ reabsorption occur and how?
PCT (67%) passively and paracellularly
In a low K+ diet does K reabsorption increase or does potassium secretion decrease?
Potassium secretion decreases in the principal cells of the DCT and the cortical collecting duct.
Name 3 ways in which aldosterone stimulates K+ secretion.
Stimulates ENaC
Stimulates Na K ATPase
Stimulates apical K+ channels
Expression
What affect does acidosis have on secretion of K+?
Inhibits K+ secretion
Through Na K ATPase inhibition
Decreased K channel permeability to K+
Name 2 luminal factors that affect K+ secretion.
Increased distal tubular flow rate - washes away luminal K+ and increases the K loss due to maintenance of a gradient
Increased Na delivery to DCT - more Na is absorbed - more K+ is lost
Why does hyperkalemia lead to less excitability of cardiac tissue?
Depolarisation - increased resting membrane potential
More fast Na channels will be in inactive state
Name a GI manifestation of hyperkalemia.
Paralytic ileus
Give some causes of hypokalemia.
External balance issues
- D/V
- Renal loss - osmotic diuresis, diuretics, high aldosterone levels
Metabolic alkalosis
Describe ECG changes that can be seen in hypokalemia.
Flat T
U wave
St depression
TUST
