A nerve cell that is stimulated by physical, chemical, or thermal insult to body tissues. When it encounters damaging or potentially damaging stimuli, the nociceptor sends signals of a possible threat to the spinal cord and brain to trigger a reflexive withdrawal from the stimulus and to rev up the body’s autonomic “fight or flight” response.

Nociceptors are found in any area of the body that can detect harmful stimuli, including the skin, muscles, joints, bladder, and gastrointestinal tract. Thermal nociceptors are activated by extreme heat or cold. Mechanical nociceptors respond to such stimuli as excess pressure and incisions that break the skin. Chemical receptors respond to environmental irritants such as cigarette smoke, spider venom, and a variety of spices — especially capsaicin, which is found abundantly in hot peppers. Sleeping/silent nociceptors refer to nociceptors that do not respond to chemical, thermal, or chemical stimuli unless an injury has already occurred.

When inflammation is present, as from rheumatic diseases like arthritis, nociceptors can respond to non-painful stimuli such as touching as if they are painful stimuli (a condition called allodynia) or overreact to painful stimuli (hyperalgesia). Nociceptive pain also occurs in tenosynovitis, compressive neuropathies such as herniated vertebral disks and carpal tunnel syndrome, bursitis, and various localized forms of arthritis.

Want to learn more pain-related terms? See our Definitions section.

Robert S. Dinsmoor is a medical writer and editor based in Massachusetts.

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