A gap between successive segments of the myelin sheath where the axon membrane is exposed is called the ...

A gap between successive segments of the myelin sheath where the axon membrane is exposed is called the ...

• A. Node of Ranvier
• B. Cleft
• C. Nucleus
• D. Myelin sheath

Answer: (A)

Gaps in a myelinated axon where the membrane is exposed are called Nodes of Ranvier. These nodes are spaced along the axon and are rich in voltage-gated sodium channels, which let the action potential be regenerated as it hops from node to node. This setup enables saltatory conduction, speeding up neural signaling compared with unmyelinated fibers. A synaptic cleft is a gap at a synapse between neurons, a nucleus is a cell-body structure containing genetic material, and the myelin sheath is the insulating covering around the axon—not a gap. So the exposed gaps between myelin segments are the Nodes of Ranvier.

Gaps in a myelinated axon where the membrane is exposed are called Nodes of Ranvier. These nodes are spaced along the axon and are rich in voltage-gated sodium channels, which let the action potential be regenerated as it hops from node to node. This setup enables saltatory conduction, speeding up neural signaling compared with unmyelinated fibers. A synaptic cleft is a gap at a synapse between neurons, a nucleus is a cell-body structure containing genetic material, and the myelin sheath is the insulating covering around the axon—not a gap. So the exposed gaps between myelin segments are the Nodes of Ranvier.