Gate Control Theory — MFDS Part 1 MCQ
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Correct answer: E — Large-diameter Aβ afferents recruit inhibitory dorsal horn interneurons, suppressing Aδ- and C-fibre nociceptive transmission
Option E is correct. Rubbing activates low-threshold, large-diameter Aβ mechanoreceptive afferents. In gate control theory, this input recruits inhibitory interneuronal circuitry in the dorsal horn and reduces onward transmission generated by small-diameter Aδ and C nociceptive afferents, thereby “closing” the gate. This accounts for transient analgesia from touch or pressure near an injury. Option A reverses the fibre roles: C fibres are nociceptive and favour transmission rather than inhibition of Aβ input. Option C is too peripheral; the defining mechanism is segmental central modulation, not nociceptor adaptation. Option B is false because descending pathways can influence the gate. Option D is false because these fibre classes differ in modality and their effects on dorsal horn circuitry.
Reference: Machi A, Patel A, Ottestad E. Nerve stimulation and neuromodulation for painful nerves: a narrative review. International Orthopaedics. 2025;49(5):989–996. https://pubmed.ncbi.nlm.nih.gov/40111452/