Pain Physiology — MFDS Part 1 MCQ

Instant feedback + full explanation. One question, done properly.

EasyPhysiologyPain PhysiologyMFDS Part 1

Following a brief noxious cutaneous stimulus, which type of primary afferent nerve fibre principally mediates the initial sharp, well-localised “first pain”?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: E — A-delta fibres

A-delta fibres are thinly myelinated, relatively fast-conducting primary afferents that principally mediate the initial sharp, well-localised “first pain” following a noxious stimulus. C fibres are unmyelinated and slower; they mediate the later burning, aching or throbbing “second pain”, which is less precisely localised. A-beta fibres predominantly transmit low-threshold touch, pressure and vibration, although specialised exceptions exist. A-alpha fibres are large, rapidly conducting fibres principally associated with proprioception and somatic motor function. B fibres are small myelinated preganglionic autonomic fibres rather than the principal afferents for cutaneous nociception.

Reference: Sikandar S, Dickenson AH. Visceral versus somatic pain: an educational review of anatomy and clinical implications—Somatic pain, Transmission. Regional Anesthesia & Pain Medicine. 2021;46:629–636. https://rapm.bmj.com/content/46/7/629