The tutor offers a summary of how a nerve impulse propagates.

The cells that carry nerve impulses are called neurons. Neurons have long conduits through which the impulses travel. A nerve impulse, as it conducts along a neuron, can be called an action potential. At the point of progress, the potential difference (aka voltage) swings from -65mV (rest potential) to +40mV (action potential) back to -65mV (rest potential).

The voltage refers to the potential difference across the cell membrane. It is managed by deployment of ions. The swing from -65mV to +40mV is accomplished by sudden controlled migration of Na+ ions into the cell. The return swing from +40mV to -65mV results from controlled departure of K+ ions. (The neuron controls when those ions can cross its membrane.)

After the action potential, the ions need to be reset so they are ready to propagate the next one. The Na+ ions are put back outside, while the K+ ions are brought back inside. This period can be referred to as the refractory period. The neuron may not be able to “fire” again until its completion.

HTH:)

Source:

Mader, Sylvia S. Inquiry into Life, 9th Ed. Toronto: McGraw-Hill, 2000.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.