Pain is a perception that alerts us to injury and triggers various compensatory behavioral responses. The sensation of pain is a complex experience that is the culmination of many events processed both centrally and peripherally. Several thalamic nuclei and cortical areas are involved in processing pain sensation (Basbaum & Jessell, 2000). Recently significant advances have been made in understanding the molecular mechanisms underlying pain perception. This process, referred to as nociception, is the means which primary sensory neurons detect painful stimuli. Various physiological and pathological states alter our perception of pain. Under certain circumstances, pain no longer serves as a warning system, instead becoming chronic and debilitating. In other instances, one's ability to sense noxious stimuli can become dulled or completely silenced, thus nullifying an inherent need for an organism to interact with its environment and respond to adverse stimuli. Adaptations in central processing play a role in these changes, but a number of mechanisms responsible occur at the level of primary sensory afferents (Raja etal., 1999).
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