Regulation of ECF Potassium Flashcards
What is the most important function of ECF potassium concentration?
The ECF potassium concentration determines the resting membrane potential of all excitable cells.
What is the most abundant ion within cells?
Potassium is the most abundant ion within a cell.
Makes sense, since we’re talking about potassium this lecture.
What is the normal range for ECF [K+]?
3.5-5.0mM
Is potassium reabsorbed or secreted?
BOTH!!!
What happens regarding potassium reabsorption in the proximal components?
Nearly complete obligatory reabsorption.
In the proximal tubule, how does potassium move from the lumen?
Potassium moves through the tight junctions by passive diffusion, driven by the flow of water.
In the LoH, how does potassium move from the lumen?
Potassium moves through the Na/K/2Cl transporter, then passively down the electrochemical gradient and out the basolateral side.
What is the first step of potassium secretion?
Movement across the basolateral membrane via the Na/K pump.
What is the second step of potassium secretion?
Passive flow down the electrochemical gradient.
In SIMPLE terms, what happens in the las of mass action?
A change in ECF concentration will drive a change in its overall tubular secretion.
What is the mechanism behind the law of mass action?
More potassium will make the Na/K ATP-ase run faster, more potassium will accumulate in the cell, then more will be excreted.
T/F: The law of mass action works on even small changes in [K+]
F. It is most effective for rather large changes in [K+]
What about hormonal regulation via aldosterone?
Increased [K+] acts upon the zona glomerulosa cells to increase aldosterone secretion
How does aldosterone effect potassium secretion?
- Aldosterone expression leads to more Na/K Atp-ase.
- Aldosterone also induces more apical sodium channels that can counter the outflow of potassium.
- Aldosterone increases the number or apical potassium channels.
Is more potassium secreted with fast or slow tubular flow?
Slow
