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).
Actions potentials in your brain are like the signal the PS4 sends to the TV or the controller sends to the PS4. They are the signals that constitute the message. An action potential is always the same strength and the same speed, but it can vary in frequency and duration. Think of action potentials as forming a sort of morse code, of fast or slow succeeding signals for a specific amount of time.