The anatomy of pain

Pain is a sensory and emotional experience that is personal and unique to an individual. Nociception is different from pain and considers the neural process of encoding and processing noxious stimuli. Anatomically noxious stimuli are transduced by nociceptors to an electrical signal carried by first-order neurons to the dorsal horn of the spinal cord. From the spinal cord second-order neurons project in tracts to the thalamus, where third-order neurons continue to higher cerebral centres. There is no known primary pain processing centre in the brain, instead multiple different areas activate and interact in response to noxious stimuli. The brain centres associated with pain perception overlap with those involved in depression. The brain regulates the nociceptive information it receives and can exert both anti- and pro-nociceptive influence. Pathology in the peripheral and central nervous systems can contribute to nociception and pain, as can changes in the interaction of higher cerebral centres. Appreciating the anatomical structures involved in pain and nociception affords an understanding of where different therapies may be applied to alleviate pain.