Which statement best describes an action potential?

Which statement best describes an action potential?

• A. The rapid change in cell membrane potential essential for cell-to-cell communication
• B. The process of DNA replication
• C. The breakdown of glucose during glycolysis
• D. The release of hormones into the bloodstream

Answer: (A)

An action potential is an electrical signal: a rapid, all-or-none change in the neuron's membrane potential that travels along the axon to enable cell-to-cell communication. It starts when depolarization brings the membrane to a threshold, opening voltage-gated Na+ channels and causing a swift influx of sodium ions that drives the membrane potential up (depolarization). Then Na+ channels close and voltage-gated K+ channels open, allowing potassium to exit and the membrane to repolarize, often briefly undershooting the resting potential (hyperpolarization) before the system is reset by pumps and leak channels. This sequence propagates down the axon without decreasing in amplitude, so the signal remains strong as it moves to synapses to trigger downstream responses. In contrast, DNA replication is the copying of genetic material, glycolysis is the metabolic breakdown of glucose for energy, and hormone release into the bloodstream is an endocrine process that does not rely on this rapid electrical membrane event.

An action potential is an electrical signal: a rapid, all-or-none change in the neuron's membrane potential that travels along the axon to enable cell-to-cell communication. It starts when depolarization brings the membrane to a threshold, opening voltage-gated Na+ channels and causing a swift influx of sodium ions that drives the membrane potential up (depolarization). Then Na+ channels close and voltage-gated K+ channels open, allowing potassium to exit and the membrane to repolarize, often briefly undershooting the resting potential (hyperpolarization) before the system is reset by pumps and leak channels. This sequence propagates down the axon without decreasing in amplitude, so the signal remains strong as it moves to synapses to trigger downstream responses.

In contrast, DNA replication is the copying of genetic material, glycolysis is the metabolic breakdown of glucose for energy, and hormone release into the bloodstream is an endocrine process that does not rely on this rapid electrical membrane event.