Advanced Placement (AP) Biology Practice Exam

What defines an action potential in neuronal communication?

1. A neural impulse that travels down an axon

2. A type of cell division in prokaryotes

3. A series of checkpoints in the cell cycle

4. A chromosomal structure facilitating mitosis

The correct answer is: A neural impulse that travels down an axon

An action potential in neuronal communication is defined as a neural impulse that travels down an axon. This phenomenon occurs when a neuron receives a sufficient stimulus, leading to a rapid change in membrane potential. Specifically, during an action potential, sodium channels open, allowing sodium ions to rush into the neuron, causing depolarization. This is followed by the opening of potassium channels, which allows potassium ions to exit the neuron, leading to repolarization. The action potential propagates along the axon, allowing the transmission of signals over long distances within the nervous system. The rapid change in voltage across the membrane is critical for the initiation and propagation of neuronal signaling, enabling communication between neurons and ultimately coordinating bodily functions.