Saltatory conduction in myelinated nerves occurs because voltage-gated sodium channels are concentrated at specific sites along the axon. At which site are these channels clustered, and what glial process seals the adjacent paranodal myelin to the axon?

• A Juxtaparanodes; tight junctions between oligodendrocyte processes
• B Internodes; desmosomes between successive Schwann cells
• C Schmidt-Lanterman incisures; hemidesmosomes anchoring myelin to basal lamina
• D Nodes of Ranvier; septate-like junctions formed by Schwann cell loops via neurofascin contactin complexes ✓

Explanation

Nodes of Ranvier carry a high density of voltage-gated sodium channels enabling saltatory conduction. Paranodal loops of the Schwann cell are attached to the axolemma by septate-like junctions involving neurofascin 155, contactin and Caspr. Internodes are channel-poor, which eliminates option B.

Reference: Basic Neurochemistry, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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