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.