Pathophysiology of Pain and Pain Pathways

Pain is a distressing experience and an important cause of suffering and disability. Pain usually signals the presence of injury or disease and generates a complex physiologic and emotional response. It has a protective function in order to restore homeostasis at the autonomic and psychological levels. This chapter reviews the physiology and mechanisms of pain, as well as the pathways in the central and peripheral nervous system that transmit nociceptive information. The chapter divides the pain anatomical pathways into the peripheral nervous system, the spinal cord with the medullary dorsal horn system, and the ascending and supraspinal system. The authors explain the pain pathways as a three-neuron pathway that carries noxious information from the periphery to the cerebral cortex. This chapter defines important concepts such as sensitization, hyperalgesia, and allodynia, as well as describes the modulation process of nociception.