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Calculate the equilibrium potentials of potassium during normo-,

hypo- (2mM) and hyperkalemia (7mM) and explain why the normal
resting membrane potential is not -90mV.

User Noomz
by
7.5k points

1 Answer

1 vote

Final answer:

Equilibrium potentials of potassium in different conditions of kalemia can be calculated using the Nernst equation. The normal resting membrane potential is approximately -70 mV due to combined potassium ion permeability, leakage of sodium ions, and the actions of the sodium-potassium pump.

Step-by-step explanation:

The equilibrium potentials of potassium can be calculated using the Nernst equation, which takes into account the concentration of potassium ions inside and outside the cell. Normokalemia typically has a potassium concentration of around 4 mM inside and 140 mM outside which yields an equilibrium potential close to -94 mV (using the Nernst equation at 37°C, factoring in the natural log of the ion concentration ratio).

During hypokalemia, when the external K+ concentration is 2 mM instead of the normal value, the equilibrium potential of potassium will become more negative than -94 mV. Conversely, with hyperkalemia at 7 mM, the equilibrium potential of potassium will be less negative. However, the normal resting membrane potential is not -94 mV but approximately -70 mV due to the cell membrane being more permeable to potassium ions than sodium ions but not exclusively permeable, allowing some sodium ions to enter the cell. Moreover, the sodium-potassium pump, which expels more positive charges from the cell than it brings in, also maintains this resting potential.

User Jonathan Marin
by
8.2k points
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