thermonociceptor

Thermonociceptor is a type of peripheral sensory neuron specialized for detecting noxious thermal stimuli and conveying pain signals. It is distinguished from non-noxious thermoreceptors that monitor ambient temperature without necessarily triggering pain.

Physiology: Thermonociceptors are typically small-diameter fibers (Aδ and C fibers) whose peripheral terminals reside in skin, mucosa, joints, and some visceral tissues. Thermal stimuli are transduced by ion channels that respond to high or low temperatures, including heat-activated TRP channels such as TRPV1 and TRPV2, and cold-sensing channels such as TRPA1 and, in some cases, TRPM8. Many thermonociceptors are polymodal, meaning they respond to mechanical or chemical stimuli in addition to temperature.

Signal transmission: Nociceptive neurons project from the peripheral terminal to dorsal root (or cranial nerve) ganglia, then to the dorsal horn of the spinal cord, and onward to thalamic and cortical pain-processing areas. Aδ fibers convey fast, sharp pain; C fibers convey slower, dull, burning pain.

Clinical relevance: Thermal nociception is essential for protective reflexes and injury avoidance. Inflammation or nerve injury can sensitize thermonociceptors, lowering thresholds and producing hyperalgesia or allodynia. Pharmacological targets include TRP channels and related signaling molecules; capsaicin and related agents selectively desensitize certain heat-sensitive nociceptors.

Note: The term thermonociceptor is sometimes used synonymously with thermal nociceptor or heat/cold nociceptor, emphasizing its role in detecting noxious temperatures.