What is the descending portion of an action potential after the initial spike potential in a cell is cause by?
A. Sodium influx into the cell.
B. Sodium efflux out of the cell.
C. Potassium influx into the cell.
D. Potassium efflux out of the cell.
A large efflux of potassium (K+) our of the cell results in a fall in electrical potential within the cell. Potassium, in high concentration intracellularly, easily leaves the cell, whereas sodium in high concentration extracellulary, will not diffuse out of the cell rapidly.