Gaps in a myelinated nerve axon are often called____________.

Gaps in a myelinated nerve axon are often called____________.

• A. Summation zones
• B. Endoneurons
• C. Axon terminals
• D. Nodes of Ranvier

Answer: (D)

Gaps in a myelinated nerve axon are called nodes of Ranvier. These gaps lack myelin and are spaced along the axon so that voltage-gated sodium channels concentrate there, allowing the action potential to be regenerated at each node. This setup enables saltatory conduction, where the nerve impulse jumps from node to node, greatly speeding transmission compared with continuous conduction along a fully myelinated fiber. The other terms refer to different structures or processes: summation zones are where multiple inputs are integrated on the postsynaptic membrane; endoneurium surrounds individual nerve fibers; axon terminals are the ends of the axon where neurotransmitters are released.

Gaps in a myelinated nerve axon are called nodes of Ranvier. These gaps lack myelin and are spaced along the axon so that voltage-gated sodium channels concentrate there, allowing the action potential to be regenerated at each node. This setup enables saltatory conduction, where the nerve impulse jumps from node to node, greatly speeding transmission compared with continuous conduction along a fully myelinated fiber. The other terms refer to different structures or processes: summation zones are where multiple inputs are integrated on the postsynaptic membrane; endoneurium surrounds individual nerve fibers; axon terminals are the ends of the axon where neurotransmitters are released.