APA Dictionary of Psychology

a membrane protein that uses energy to actively transport sodium ions out of a cell against their concentration gradient. The main sodium pump responsible for maintaining the resting potential of animal cells, and hence the excitability of neurons and muscle cells, is called an Na+/K+ ATPase. In each cycle, this pump moves three sodium ions out of the cell, across the plasma membrane, in exchange for two potassium ions entering the cell, using energy derived from ATP.