The Resting Membrane Potential

The resting membrane potential is the difference in electrical potential between the inside and outside of the cell membrane of neurons at rest when they are not being stimulated. Typically, the value is around negative 70 millivolts, meaning that it is more negative inside.

Cell membranes are selectively permeable because most ions and molecules cannot passively diffuse across them. They often require transmembrane proteins, such as ion channels, to allow them to pass through. When a neuron is at rest, potassium channels are the main type of ion channel that are open.

Another transmembrane protein, the sodium potassium pump, uses energy to continuously move sodium out of the cell, and potassium in. This action creates a concentration gradient, with a higher concentration of potassium inside than outside.

The force of diffusion then causes potassium ions to move down their concentration gradient, through the open potassium channels, and out of the cell. The movement of these positive ions out combined with negatively charged proteins inside the cell creates a negative charge inside the membrane, a negative potential when a neuron is at rest.