Final answer:
An action potential is the rapid change in electrical charge across a neuron's membrane that transmits a nerve impulse along the axon. It occurs when the normally negatively charged interior of the neuron becomes positive due to the influx of sodium ions, after which the impulse travels down the axon, similarly to an electrical current.
Step-by-step explanation:
What is an Action Potential in Psychology?
An action potential is a fundamental concept in neurobiology that is critical to understanding how neurons communicate. When a neuron is at rest, the inside of the cell is negatively charged relative to the outside. Upon receiving a stimulus, there is a rapid change in electrical charge across the neuron's membrane, known as depolarization. Positive sodium ions flood into the cell, causing the inner membrane potential to become positive compared to the outside. This initiates the action potential, which is a reversal of electrical charge that propagates along the axon as a nerve impulse.
The process continues as the membrane depolarizes the adjacent section of the axon, creating a wave-like effect that transmits the action potential down the axon. As the action potential travels, it triggers the opening and closing of ion channels along the axon's membrane, allowing the impulse to move steadily. Muscle cells can also produce action potentials for contraction.
In terms of quantification, the change in membrane voltage during an action potential is substantial: from around -70 mV at rest to +30 mV during depolarization, amounting to a 100 mV change or 0.1 V. Although this seems small compared to the voltages seen in batteries, like the 1.5 V in an AA battery or 9 V in a rectangular battery, it is critical for neuronal function.