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 occurs as a result of a stimulus to the neuron This means that some event (a stimulus) causes the resting potential to move toward 0 mV When a neuron is not sending a signal, it is at rest..hen a neuron is at rest, the inside of the neuron is negative relative to the outside Action potentials are caused by an exchange of ions across the neuron membrane. A stimulus first causes sodium channels to open.