Generation and propagation of the action potential.

The action potential is a regenerative electrical phenomenon observed on excitable cell membranes that allows the propagation of signals without attenuation. It is the cornerstone of neurophysiology. This chapter is a review of the action potential and its relationship to the signals that are studied in clinical neurophysiology. The first section traces the history of key scientific discoveries over the last 250 years that have led to our present-day understanding of the electrical properties of nerve and muscle. The second section considers the molecular and biophysical mechanisms that are responsible for the electrical potentials that can be measured across all eukaryotic cell membranes, but specifically in neurons, nerves, and muscle. Mechanisms underlying propagation action potentials within the nervous system are also examined. The concluding section is a brief overview of the normal "macroscopic" signals that are commonly recorded from the central and peripheral nervous system, and how they are derived from action potentials.