Neurons rely on a number of mechanisms to perform their important jobs of (i) receiving information, (ii) information processing, (iii) signal propagation, and (iv) signal transmission. One such mechanism that is at the core of neuronal function is based on rapid and reversible reversal of the electrical potential difference across the plasma membrane. By reversal, it is meant that the membrane potential rapidly changes from its resting level of approximately −70 mV to around +50 mV and, subsequently, rapidly returns to the resting level again. The rapid reversal of membrane potential forms an important basis for information processing, propagation, and transmission and is referred to as the action potential, electrical impulse, or nervous impulse. In this fashion, neurons are said to be excitable cells. The focus of this lecture is to learn about the details of the neuronal action potential. Neurons are not the only excitable cells in the human body. Muscle cells (skeletal, cardiac, and smooth muscle), and some endocrine cells (i.e., hormone producing cells) are also excitable (i.e., exhibit action potentials). These cells will be discussed in later lectures.

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