Pain is an unpleasant experience that results from both physical and psychological responses to injury. A complex set of pathways transmits pain messages from the periphery to the central nervous system, where control occurs from higher centres. Primary afferent pain fibres synapse with second-order neurons in the dorsal horn of the spinal cord. Ascending spinothalamic and spinoreticular tracts convey pain up to the brain, where pain signals are processed by the thalamus and sent to the cortex. Descending tracts, via the midbrain periaquaductal grey and nucleus raphe magnus, have a role in pain modulation. When nerves are damaged, neuropathic pain results and various mechanisms have been proposed for how this takes place. These mechanisms involve both peripheral and central sensitization. inthis study we tried to focus on the various types of pain, pain receptors and their stimulation causes of pain the main aspects of our article specifies Surgical interruption of pain pathways and Special Capability of pain signals to arouse overall brain excitability , Brain opiate system Gate control theory of pain suppression and Localization of referred pain transmitted via the visceral pathway.

Conclusion: The neurobiology of pain is continuously being explored and the novel therapeutic targets for pain relief are being tested. The multiple complex circuitries of the pain pathway, with central and peripheral modulation of the perception, make it a very complex sensation with sensory, cognitive and emotional components associated with it. This article gives a broad overview of the physiology of pain. It explains pain as a complex experience involving both physical and psychological adaptations. The normal pain pathways are described in some detail in a systematic fashion from nociceptor to central nervous system and back to periphery

Keywords: Central sensitization; gate-control theory; neuropathic pain; nociception; pain pathways; peripheral sensitization; somatic pain; visceral pain.

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Dr A.B. Solepure

Dean IIMSR Medical College