Osmosis video - Resting membrane potential

The resting membrane potential (RMP) is the electrical potential difference across the plasma membrane of a cell when the cell is at rest and not undergoing any significant electrical activity. This potential difference is created by the unequal distribution of ions across the membrane, with positively charged ions (such as sodium and calcium) being more concentrated outside the cell and negatively charged ions (such as chloride and potassium) being more concentrated inside the cell.

Each ion has its own equilibrium potential, which is determined by the Nernst equation. It states that an ion's resting membrane potential (Vm) equals 61.5 times the log of the concentration of the ion outside the cell, divided by the concentration of the ion inside the cell, for an ion with a single charge like sodium, and Vm equals 30.75 times the log the concentration of the ion outside divided by the concentration of the ion inside for an ion with a double charge like calcium.

Vm = 61.5Log [ION]out[ION]in for single charged ions (E.g. Na+) Vm = 30.75Log [ION]out[ION]in for double charged ions (E.g. Ca2+) The cell's resting membrane potential will therefore be the summation of each individual ion's equilibrium potential.