What is the action potential?

An action potential is part of the process that occurs during the firing of a neuron.
During the action potential, part of the neural membrane opens to allow positively charged ions inside the cell and negatively charged ions out.

This process causes a rapid increase in the positive charge of the nerve fiber. When the charge reaches +40 mv, the impulse is propagated down the nerve fiber.

This electrical impulse is carried down the nerve through a series of action potentials.




In animal cells, there are two primary types of action potentials, one type generated by voltage-gated sodium channels, the other by voltage-gated calcium channels.

Sodium-based action potentials usually last for less than one millisecond, whereas calcium-based action potentials may last for 100 milliseconds or longer.

In some types of neurons, slow calcium spikes provide the driving force for a long burst of rapidly-emitted sodium spikes.

In cardiac muscle cells, on the other hand, an initial fast sodium spike provides a "primer" to provoke the rapid onset of a calcium spike, which then produces muscle contraction.