Saltatory conduction describes the rapid conduction of impulses along what type of nerve fibers?

Saltatory conduction describes the rapid conduction of impulses along what type of nerve fibers?

• A. Myelinated
• B. Unmyelinated
• C. Both equally
• D. None

Answer: (A)

Saltatory conduction is the rapid transmission of nerve impulses along myelinated fibers. The myelin sheath serves as an insulator around the axon, and voltage-gated sodium channels are concentrated at the gaps between myelin sheaths, called nodes of Ranvier. When an action potential is generated, depolarization at one node triggers a current that quickly depolarizes the next node, so the impulse appears to “jump” from node to node while the insulated stretches in between don’t require ion flow. This skipping of the membrane segments speeds up conduction because ions move only at the nodes, not along every millimeter of axon. In contrast, unmyelinated fibers conduct the impulse continuously along the entire membrane, which is slower since depolarization must occur across every patch of membrane as the impulse travels. The presence of myelin and the nodal architecture thus explains why myelinated fibers transmit impulses more rapidly, and why diseases that demyelinate axons slow or block conduction.

Saltatory conduction is the rapid transmission of nerve impulses along myelinated fibers. The myelin sheath serves as an insulator around the axon, and voltage-gated sodium channels are concentrated at the gaps between myelin sheaths, called nodes of Ranvier. When an action potential is generated, depolarization at one node triggers a current that quickly depolarizes the next node, so the impulse appears to “jump” from node to node while the insulated stretches in between don’t require ion flow. This skipping of the membrane segments speeds up conduction because ions move only at the nodes, not along every millimeter of axon.

In contrast, unmyelinated fibers conduct the impulse continuously along the entire membrane, which is slower since depolarization must occur across every patch of membrane as the impulse travels. The presence of myelin and the nodal architecture thus explains why myelinated fibers transmit impulses more rapidly, and why diseases that demyelinate axons slow or block conduction.