Sensory systems I

Chemical mediators can sensitize and sometimes activate the peripheral endings of nociceptors. Injury or tissue damage releases bradykinin and prostaglandins, both of which activate and sensitize nociceptors. Activation of nociceptors leads to the release of substance P and other peptides. Substance P acts on mast cells in the vicinity of sensory endings to evoke degranulation and the release of histamine, which directly excites nociceptors.