Modified: 2020-06-09
In the vast majority of animals, including humans, nerve conduction is an electro-chemical process. It is electric within the neuron and chemical between neurons. Within the neuron it is the process of depolarization that makes it electrical. Note that it is not much electricity; the charge difference is about -70 millivolts.
What does depolarization mean? Think of a car battery; it has two poles. One is labelled (+) and one is labelled (-). That battery is polarized; you can depolarize it (do not do this, you will be sorry) by connecting a wire to each pole and touching them together. Sparks will fly, and electricity will flow.
When the neuron is at rest, when it is not conducting a nerve impulse or action potential, it is polarized. That polarization is accomplished by the separation of sodium (Na) and potassium (K) ions by the neuron's cell membrane. The action potential consists of the invasion of the cell by the Na ions and the simultaneous expulsion of the K ions. So the electric charge difference is momentarily gone. This process continues down the axon so that the effect is like a wave of depolarization.
A good example of depolarization is a string of firecrackers. If you watch them go off from a distance it looks like a continuous, moving explosion. I actuality it is a series of individual firecrackers going off one after the other. The same is true in the axon. Each exchange of Na and K ions is akin to a tiny, local explosion.
When the depolarization reaches the terminal buttons, it causes neurotransmitters to be released into the synapse. Those neurotransmitters either excite or inhibit the post-synaptic neuron. If they excite it, then the action potential will continue on the post-synaptic neuron. If they inhibit it, then the action potential will stop.