The function of the myelin sheath that surrounds many neurons is to

• A. Increase the rate of impulse transport
• B. Provide nutrients to the neuron
• C. Store energy
• D. Transmit signals across synapses

Answer: (A)

The myelin sheath acts as electrical insulation around many axons, which speeds up how quickly nerve signals travel. By wrapping the axon, it reduces the leakage of current and increases membrane resistance, so the depolarizing signal doesn’t fade as it moves. The gaps between the wrapped sections, the nodes of Ranvier, allow the action potential to be regenerated at each node, letting the impulse “jump” from node to node in a process called saltatory conduction. This makes transmission much faster than along an unmyelinated fiber. It doesn’t provide nutrients, store energy, or transmit signals across synapses—that final step happens at the synapse via neurotransmitters.