What are the gaps in a myelinated axon that enable saltatory conduction called?

What are the gaps in a myelinated axon that enable saltatory conduction called?

• A. Axon hillocks
• B. Nodes of Ranvier
• C. Synaptic boutons
• D. Nissl bodies

Answer: (B)

Gaps in a myelinated axon are called nodes of Ranvier. These exposed segments between myelin sheaths host a high density of voltage-gated sodium channels, so when the action potential reaches a node, it is re-initiated there. The electrical signal then travels quickly through the insulated internodes to the next node, where it triggers another spike. This setup—saltatory conduction—greatly speeds up signaling because the myelin increases membrane resistance and lowers capacitance, allowing current to jump from node to node rather than depolarizing every point along the membrane. Other terms refer to different neuronal structures: the axon hillock is where action potentials often start, synaptic boutons are at axon terminals for neurotransmitter release, and Nissl bodies are rough endoplasmic reticulum in the soma.

Gaps in a myelinated axon are called nodes of Ranvier. These exposed segments between myelin sheaths host a high density of voltage-gated sodium channels, so when the action potential reaches a node, it is re-initiated there. The electrical signal then travels quickly through the insulated internodes to the next node, where it triggers another spike. This setup—saltatory conduction—greatly speeds up signaling because the myelin increases membrane resistance and lowers capacitance, allowing current to jump from node to node rather than depolarizing every point along the membrane. Other terms refer to different neuronal structures: the axon hillock is where action potentials often start, synaptic boutons are at axon terminals for neurotransmitter release, and Nissl bodies are rough endoplasmic reticulum in the soma.