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).
Action Potential Explained - The Neuron. An Action potential is the neurons way of transporting electrical signals from one cell to the next. This is a picture of a neuron, where you have dendrites in one end, and the axon terminal in the other end. In the middle of the neuron you will find the axon, which is where the electrical signal will travel from the dendrites to the axon terminal to the synapse.