The substantia gelatinosa of Rolando in the spinal cord receives which primary afferent fibers and modulates which sensory modality?
- A A-delta and C fibers; pain and temperature ✓
- B A-beta fibers; vibration and proprioception
- C A-alpha fibers; muscle stretch
- D A-delta fibers; pressure from skin
Correct answer: A. A-delta and C fibers; pain and temperature
Explanation
The substantia gelatinosa (lamina II of Rexed) at the apex of the dorsal horn receives small-diameter myelinated A-delta and unmyelinated C fibers carrying pain and temperature signals. It contains enkephalinergic interneurons that modulate pain transmission — the basis of the gate-control theory. A-beta fibers subserving touch and vibration primarily synapse in laminae III-V. The substantia gelatinosa surrounds the zone of Lissauer and is distinct from the nucleus proprius (laminae III-IV) below it.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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