How does myelination affect conduction velocity?

How does myelination affect conduction velocity?

• A. It has no impact on conduction speed.
• B. It increases conduction velocity via saltatory conduction.
• C. It slows conduction by increasing capacitance.
• D. It reduces the amplitude of action potentials.

Answer: (B)

Myelination speeds how fast a nerve impulse travels by enabling saltatory conduction. The myelin sheath acts as insulation, increasing the membrane’s resistance and dramatically reducing its capacitance. With higher resistance and lower capacitance, less current leaks across the membrane, so the depolarizing signal can travel quickly along the insulated segments. Because voltage-gated Na+ channels are concentrated at the nodes of Ranvier, the action potential is regenerated there, causing the impulse to leap from node to node rather than propagate continuously along the entire axon. This jumping mechanism greatly shortens the distance over which active depolarization must occur, boosting conduction velocity. The amplitude of the action potential is preserved at each node since it is regenerated, while the insulated internodes simply conduct the signal passively. In contrast, unmyelinated fibers experience slower conduction because current leaks across the membrane along the entire length, requiring more time to depolarize each segment.

Myelination speeds how fast a nerve impulse travels by enabling saltatory conduction. The myelin sheath acts as insulation, increasing the membrane’s resistance and dramatically reducing its capacitance. With higher resistance and lower capacitance, less current leaks across the membrane, so the depolarizing signal can travel quickly along the insulated segments. Because voltage-gated Na+ channels are concentrated at the nodes of Ranvier, the action potential is regenerated there, causing the impulse to leap from node to node rather than propagate continuously along the entire axon. This jumping mechanism greatly shortens the distance over which active depolarization must occur, boosting conduction velocity. The amplitude of the action potential is preserved at each node since it is regenerated, while the insulated internodes simply conduct the signal passively. In contrast, unmyelinated fibers experience slower conduction because current leaks across the membrane along the entire length, requiring more time to depolarize each segment.