PS263 Chapter Notes - Chapter 1: Resting Potential, Saltatory Conduction, Myelin
Document Summary
Stimulation beyond the threshold of excitation produces massive depolarization of the membrane. When potential reaches threshold, membrane opens sodium channels. When sodium channels are open wide the electrical potential across membrane passes beyond zero to a reversed polarity. This means the inside of cell has slight positive charge vs negative. At peak of action potential, sodium gates snap shut for a millisecond. Concentration and electrical gradients drive positively charged potassium ions out of cell. Eventually enough potassium ions leave to drive membrane beyond usual resting level to temporary hyperpolarization. At end of process, membrane has returned to resting potential but inside has slightly more sodium ions and slightly fewer potassium ions. Process to restore original distribution takes time and thus neuron cannot fire again during hyperpolarization. Action potentials start in axon and back propogates into cell body and dendrites which passively register electrical event.
