ABSTRACT
Substance P, produced in the dorsal root ganglia, is transported to the peripheral nerve endings. Pain can be generated from the peripheral nervous system (PNS) and Central nervous system (CNS), including the autonomic aspects of the CNS. Sensory nerve axons have three functions: encoding, conduction, and relaying sensory information from the periphery to the CNS for processing. If any of these aspects does not function properly, the CNS may have difficulties determining the meaning of the projected information. When sprouts reach peripheral target tissue, peripheral receptor activity restarts and growth ends. Neuromas are associated with the induction of clinical pain in the peripheral nerves associated with the stumps of amputated limbs, including phantom limb pain. Primary hyperalgesia appears to occur after a reduction in the activation thresholds of nociceptors and peripheral sensitization, and is associated with thermal and mechanical hypersensitivity.
