Nociceptorok

Nociceptors are specialized sensory neurons of the peripheral nervous system that detect tissue damage and initiate the sensation of pain. They have free nerve endings located in the skin, joints, muscles, and visceral organs, and respond to potentially damaging mechanical, thermal, and chemical stimuli.

Two major functional classes of nociceptor fibers are A-delta fibers (thinly myelinated, fast, conveying sharp, well-localized pain) and C fibers (unmyelinated, slower, conveying dull, diffuse pain). Nociceptors can be polymodal, responding to multiple types of noxious stimuli.

Detection and transduction rely on ion channels and receptors such as TRP channels (e.g., TRPV1 for heat and chemical irritants), acid-sensing ion channels, and mechanosensitive channels like Piezo. Upon activation, nociceptors generate action potentials that convey signals toward the spinal cord.

In the central nervous system, signals enter the dorsal horn of the spinal cord and ascend via the spinothalamic tract to the thalamus and then to cortical areas. Pain perception is modulated by endogenous systems and can be amplified (hyperalgesia) or evoked by non-painful stimuli (allodynia) during inflammation and injury.

Clinical relevance: nociceptors are targets for analgesia. Anti-inflammatory drugs reduce sensitization by limiting prostaglandin production; local anesthetics block sodium channels to prevent action potential propagation; capsaicin desensitizes nociceptors by depleting substance P and affecting TRPV1. Understanding nociceptor function informs pain management and research.