Which rapid electrical charge traveling along an axon?

• A. Dendrite
• B. Axon
• C. Myelin Sheath
• D. Action Potential

Answer: (D)

Action potential

This is the rapid electrical impulse that travels along a neuron's axon. It starts when the neuron reaches a threshold and triggers a quick influx of sodium ions, causing depolarization, followed by potassium outflow that restores the resting state. The wave of depolarization propagates down the axon because each segment triggers the next, so the signal moves without losing amplitude. In myelinated fibers, the impulse speeds up by skipping between gaps in the myelin (nodes of Ranvier) in a process called saltatory conduction. Dendrites, by contrast, mainly receive inputs and generate graded potentials, not the rapid spike that travels along the axon. The myelin sheath speeds conduction but isn’t the electrical charge itself; the action potential is the actual rapid charge traveling along the axon.