ABSTRACT
Geddes and Baker have summarized a number of studies in which membrane potential differences have been measured under a variety of conditions in a variety of mammalian cells. The action potential occurs because the stimulus produces a localized depolarization that is propagated along the cell. Depolarization of the cell itself is due to an exchange of ions through small openings in the cell’s membrane. The propagated depolarization due to selective ionic movement may be electrically sensed in the single cell by inserting one cellular electrode inside the cell and placing a second electrode on the outside. The recorded action potential consists of several components: First, there is a small prepotential, followed by a discharge (depolarization), during which the inside of the semipermeable membrane becomes positive relative to the outside. Finally, there is a recovery (repolarization) phase during which the inside once again becomes negative relative to the outside, and the cell voltage returns to its resting membrane potential.
