Week 6 - Control of Potassium Flashcards
How is the difference between the ICF and the ECF potassium concentrations maintained?
The sodium potassium atpase
Why is the potassium concentration inside and outside the cells important?
Allows a gradient to be maintained of the cell membrane and therefore potassium moves out.
What happens if the conc of potassium in the ECF decreases?
Increase the gradient and potassium will want to move out the cell more. Potassium is positively charged. Therefore this hyperpolarises the cell - more negative
What are the 2 processes that regulate potassium?
Internal balance and external balance
Internal - moves K+ between ICF and ECF - immediate
External - adjusts renal potassium excretion
How is the internal balance of potassium achieved? Two processes
1) movement of k from ECF to ICF via nak atpase
2) movement of k out of cells into ECF via k channels - ROMK
What factors increase the uptake of potassium by cells? 3
1) hormones - insulin, aldosterone and catecholamines
2) increased potassium in ECF
3) alkalosis - low ECF h+ - h+ move out of cells to correct alkalosis and reciprocal potassium shift into cells
How does insulin increase the uptake of potassium by cells?
Increases transcription for the protein that forms nak atpase
- clinical use - given IV with dextrose to treat hyperkalaemia
How does aldosterone work to increase potassium uptake by cells?
K+ in blood stims aldosterone secretion which stimulate uptake via nak atpase ….. Find out more
Why are catecholamines used to increase potassium?
Catecholamines are released in response to stress or exercise when acid production has occurred. They act on beta 2 adenoceptors which stims sodium potassium atpase and cellular uptake of potassium
What 5 factors influence potassium shift out of cells?
Exercise Cell lysis Increase in ECF OSMOLARITY Low ECF potassium Acidosis - shift of hydrogen ions into cells = potassium out
How is potassium distributed in the body fluids?
98 percent is intracellular and the concentration is 120-150mmol
2 percent in Extracellular and concentration is 3.5 - 5
Mainly in skeletal muscle cells but also liver, rbc and bone
