A cellular process in which sodium is immediately excreted from any cell which it enters and potassium is brought in.
The energy requiring process by which a high potassium concentration is maintained inside cells and a high sodium level is maintained outside the cells. The energy is provided by ATP.
The active transport mechanism that moves sodium ions across a membrane to their area of greater concentration. In neurons and muscle cells, this is outside the cell. In many cells, the sodium pump is linked with the potassium pump that transports potassium ions into the cell, also against a concentration gradient, and may be called the sodium-potassium pump. In neurons and muscle fibers, this pump maintains the polarization of the membrane.