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).
Phase 1 of the myocyte action potential occurs with the inactivation of the fast Na+ channels. The transient net outward current causing the small downward deflection of the action potential is due to the movement of K + and Cl â ions, carried by the Ito1 and I to2 currents, respectively.