Medical Definition of antioxidant. : any of various substances (as beta-carotene, vitamin C, and alpha-tocopherol) that inhibit oxidation or reactions promoted by oxygen and peroxides and that include many held to protect the living body from the deleterious effects of free radicals.
An action potential is a very rapid change in membrane potential that occurs when a nerve cell membrane is stimulated. Specifically, the membrane potential goes from the resting potential (typically -70 mV) to some positive value (typically about +30 mV) in a very short period of time (just a few milliseconds).
An action potential is a pulse-like wave of voltage that can travel on certain types of cell membranes. It occurs most commonly on the membrane of the axon of a neuron, but also appears in other types of excitable cells, such as cardiac muscle cells and even plant cells.igure 1. A. view of an idealized action potential shows its various phases as the action potential passes a point on a cell membrane. B. Recordings of action potentials are often distorted compared to the schematic view because of variations in electrophysiological techniques used to make the recording.