At rest, there are more sodium ions on the outside of cells compared to the inside. This difference in sodium ion concentration is regulated by the sodium-potassium pump. The sodium-potassium pump is crucial for maintaining the resting membrane potential that is involved in essential processes such as propagating a neuronal action potential. The resting membrane potential of a neuron is approximately -70 mV. The sodium-potassium pump regulates the concentration gradient in a manner in which the interior of cells are low in sodium and high in potassium; K+ leaks from the inside of the cell to the outside, generating a negative charge on the inside of the membrane.