What is an action potential?

An action potential is a brief change in the membrane voltage of a neuron or muscle cell that occurs when a stimulus causes the resting membrane potential to become more positive. This change allows the cell to transmit electrical signals along its membrane, facilitating communication within the nervous system. During an action potential, sodium channels open, allowing sodium ions to flow into the cell, depolarizing the membrane. This depolarization leads to a rapid spike in voltage, followed by a repolarization phase where potassium channels open, returning the membrane to its resting state.

Understanding this concept is crucial, as it underpins how neurons transmit signals and how muscle contractions occur, ultimately playing a vital role in the functioning of the nervous system and muscle activity. The other options, while related to neural function, do not accurately define action potentials. A synapse is a junction between two neurons, neurotransmitters are chemical messengers involved in transmitting signals across synapses, and sensory receptor activation refers to the process by which sensory cells respond to stimuli. These concepts revolve around neural communication but do not capture the specific process of an action potential.