Pain is a sensation that occurs when tissue is damaged. It is transmitted by A-delta and C nerve fibers from the periphery to the spinal cord and brain. A-delta fibers allow for fast localization of pain while C fibers transmit slower and induce emotional responses. In the spinal cord, fibers synapse separately and transmit via different tracts. Modulation occurs through gate control theory in the dorsal horn and descending analgesia from the brainstem. This controls pain sensation to allow tissue repair without pain.