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).
The Action Potential [back to top]. The resting potential tells us about what happens when a neurone is at rest. An action potential occurs when a neurone sends information down an axon. This involves an explosion of electrical activity, where the nerve and muscle cells resting membrane potential changes.