Physiology & Biochemistry · single question
Pain transmitted by A-delta fibers is characterized as:
Show answer and explanation
Correct answer: B. Sharp, well-localized, and rapid in onset
- A. Dull, aching, poorly localized pain is carried by UNMYELINATED C fibers (0.5–2 m/s) — this is SECOND pain, and in the pulp it signals inflammation extending into the pulp proper (irreversible pulpitis).
- B. CORRECT. A-DELTA fibers are thinly MYELINATED and fast-conducting (5–30 m/s). They mediate FIRST pain — sharp, pricking, well-localized, and immediate. In the dental pulp they terminate in the dentinal tubule region and mediate DENTIN sensitivity, which is why they are the fibers responsible for the sharp response to cold and air.
- C. A-delta fibers are abundantly present in the pulp — they are what makes the cold test work.
- D. Burning, slow, throbbing quality is again C-fiber pain.
Note: Sharp brief pain to cold = A-delta = reversible/dentin. Dull lingering throbbing pain = C fiber = irreversible pulpitis.
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