1. An action potential is a rapid change in membrane potential that is governed by the opening and closing of ion channels in the plasma membrane of the neuron. In this tutorial, we will review the events of an action potential measured from a small area of a neuron's membrane. The action potential can be divided into five phases: the resting potential, threshold, the rising phase, the falling phase, and the recovery phase. 2. We begin with the resting potential, which is the membrane potential