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Abstract
Nociception refers to the physiological process of activation of specialized neural pathway, specifically by tissue damaging or potentially tissue damaging stimuli. Pain in contrast to nocieption is a conscious experience which may be affected by factors such as alterations in somatosensory processing or psychosocial factors.
There are three classes of primary afferent fibers in the skin that may be activated by a given cutaneous stimulus, the large diameter myelinated (A) fibers are responsible for light touch, pressure, or hair movement and have the fastest conduction velocity. The Axons of nocieptive neurons are generally unmyelinated (C fibers) or thinly myelinated (A fibers).
When a noxious stimulus produces tissue injury, chemical mediators are released and activate nocieptors which in turn generate nerve impulses. The main excitatory neurotransmitters in the somatosensory system are the amino acids glutamate and aspirate while the primary inhibitory neurotransmitters of the somatosensory system include glycine and gamma – aminobutyric acid (GABA).