Visceral pain from thoracic or abdominal organs is transmitted by which nerve fibers?

Visceral pain from thoracic or abdominal organs is transmitted by which nerve fibers?

• A. A delta fibers
• B. Myelinated type B fibers
• C. Unmyelinated type C fibers
• D. Large diameter A beta fibers

Answer: (C)

Visceral pain from thoracic or abdominal organs is transmitted mainly by unmyelinated type C fibers. These small, slow-conducting fibers carry dull, aching, poorly localized pain that is typical of internal organs. They travel with autonomic pathways to the dorsal root ganglia and into the spinal cord, which also helps explain why visceral pain often refers to somatic regions. In contrast, fast, sharp pain from many somatic structures is carried by myelinated A-delta fibers, which conduct quickly and produce well-localized sensations. The autonomic preganglionic fibers are myelinated B fibers, but they carry autonomic signals rather than nociceptive pain. Large-diameter A-beta fibers convey non-nociceptive touch and proprioception, not pain.

Visceral pain from thoracic or abdominal organs is transmitted mainly by unmyelinated type C fibers. These small, slow-conducting fibers carry dull, aching, poorly localized pain that is typical of internal organs. They travel with autonomic pathways to the dorsal root ganglia and into the spinal cord, which also helps explain why visceral pain often refers to somatic regions.

In contrast, fast, sharp pain from many somatic structures is carried by myelinated A-delta fibers, which conduct quickly and produce well-localized sensations. The autonomic preganglionic fibers are myelinated B fibers, but they carry autonomic signals rather than nociceptive pain. Large-diameter A-beta fibers convey non-nociceptive touch and proprioception, not pain.