Which fiber type conducts impulses fastest due to saltatory conduction?

• A. Unmyelinated fibers
• B. Myelinated fibers with nodes of Ranvier
• C. Small diameter fibers
• D. All fibers equally

Answer: (B)

Saltatory conduction is the rapid transmission of a nerve impulse that happens in myelinated fibers with gaps called nodes of Ranvier. The myelin sheath acts as an insulator, increasing membrane resistance and reducing membrane capacitance, so the electrical signal can race quickly along the insulated segments. The signal only needs to be refreshed at the nodes, where ion channels are concentrated, so it effectively “jumps” from node to node. This leapfrogging greatly speeds up conduction compared to continuous depolarization along unmyelinated fibers, where every tiny segment must be depolarized. Smaller diameter fibers have higher internal resistance, which slows conduction, and saying all fibers conduct equally ignores how myelination and structure matter. Thus, the fastest conduction occurs in myelinated fibers with nodes of Ranvier.