Pain sensation Pain receptors are also called as nociceptors They are located at the ends of small 'C unmyelinated or myelinated A delta fibers a) Definition Pain sensation is unpleasant but protective sensation aroused by noxious stimuli that damage or can damage body tissues b) Physiology (properties & reaction) Purpose or importance: Protective Stimulus: noxious (chemicals like- Ach, bradykinin, serotonin, hydrogen ions, potassium ions, prostaglandins or mechanical or thermal) Receptors: free nerve endings (polymodal receptors) Adaptation : non or slow adapting receptors Nerve fibers: fast pain is carried by A-delta nerve fibers while slow pain by 'C' type. Neurotransmitters: glutamic acid (at spinal cord) for fast pain, substance P (at spinal cord) for slow pain and Lewis P factor for muscle pain, Pathway: lateral spinothalamic (specific neo spinothalamic for fast pain and diffuse and non specific paleo spinothalamic for slow pain) Reaction : pain is a
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