Sodium and potassium balance (Potassium regulation) Flashcards
Potassium is the main ____ ion
intracellular
Where does extracellular potassium have effect on?
excitable membranes (nerves / muscles)
What happens when you have high extra cellular K+?
What about low extracellular K+?
High – depolarises membranes - action potentials, heart arrhythmias.
Low – heart arrhythmias (asystole)
depolarisation more difficult
When the plasma K+ is, high what stimulates it to be taken up by tissue?
insulin
+ aldosterone and adrenaline
How does insulin stimulate the uptake of extracellular potassium into the cells?
insulin stimulated the Na+/H exchanger
this increases the sodium conc in the cell, which then makes the Na+/K+/ATPase more active,
thereby taking up potassium into the cell
Explain K+ reuptake in the nephron under normal and increased potassium intake
2/3 reabsorbed in the PCT
20% reabsorbed in the thick ascending limb of LoH
DCT -> potassium secretion
CD -> potassium secretion
as a result 15-80% of potassium is excreted
Explain K+ reuptake in the nephron in potassium depletion situations
2/3 reabsorbed in PCT
20% reabsorbed in the thick ascending limb of LoH
3% reabsorbed in DCT
9% reabsorbed in CD
as a result only 1% excreted
What is potassium secretion stimulated by?
When plasma K+ levels are high, how is K+ secreted in the principal cells of the DC?
via the Na/K-ATPase (increased activity)
affect membrane potential and K+ flows into the tubule
How is tubular flow detected in the kidney and how does tubular flow affect K+ excretion?
primary cilia detect tubular flow and stimulate PDK1, which drives Ca2+ into cell, increasing the Ca2+ conc
this opens the K+ channel and more K+ flows out into the tubule
What can cause hypokalemia?
-
What can cause hyperkalemia?
-
What can cause hyperkalemia?
What is the name of the genetic syndrome that caused hypokalemia?
Gitelman’s
