An action potential is a brief event that occurs when there is a change in the membrane potential, or electrical activity, of a neuron.
Action potentials play an integral part of communication between neurons and are involved in many processes within the central nervous system, neuromuscular junctions, and cardiac functions. They occur in response to a stimulus, such as sensory input or neurotransmitters, usually through the dendrites of the neuron. These stimuli cause small excitations in the dendrites or cell body called graded potentials. Graded potentials are summated and must be strong enough to trigger the impulse. At rest, the inside of a neuron is negative relative to the outside. Once it is stimulated, the intracellular environment becomes positive relative to the outside of the cell, thus allowing ion channels to open and sodium (Na+) to move into the axon. Most neurons have a protein called myelin that surrounds segments of...
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