Define the term "action potential."

An action potential refers to a rapid, temporary change in the electrical membrane potential of a neuron, which occurs when a stimulus causes the membrane to depolarize. During an action potential, the neuron undergoes a quick sequence of events: the membrane depolarizes, reaches a threshold, and then repolarizes as sodium channels open and close, allowing sodium ions to rush in and potassium ions to exit. This process creates a brief, sharp spike in voltage that propagates along the axon, enabling the transmission of signals within the nervous system.

In contrast to the correct answer, the other options describe different aspects of neuronal behavior but do not accurately capture the definition of an action potential. For instance, a slow, gradual change in membrane potential is typically associated with local potentials or graded potentials, which also involve changes in ion concentrations but do not meet the threshold required for action potential generation. A type of neurotransmitter released does not pertain to the electrical activity of a neuron itself but rather to the chemical communication between neurons. Lastly, the resting state of a neuron describes the condition when the neuron is not firing, characterized by a stable, negative membrane potential, which is distinctly different from the active process of generating an action potential.