Which term describes the protective insulating covering around many neurons that increases conduction speed?

• A. Nucleus
• B. Axon
• C. Dendrite
• D. Myelin sheath

Answer: (D)

The key idea is that a myelin sheath acts as an insulating covering around axons to speed up signal transmission. This protective coating, produced by glial cells, wraps the axon and reduces current leakage, so electrical impulses can travel quickly. In myelinated fibers, signals are boosted at gaps called nodes of Ranvier, allowing them to jump from node to node in a process called saltatory conduction. This makes conduction much faster than along unmyelinated fibers. The other terms refer to different parts of the nerve cell (nucleus is the cell’s control center, dendrites receive signals, the axon transmits signals) and do not provide the same insulation to boost speed.