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PAIN

 

            Pain is an unpleasant sensory and the emotional experience associated with actual or potential tissue damage. It alerts us to danger and tells us when something is wrong within our bodies. If danger is acute the body may react even before the brain is aware of the danger. For example the reflex action of jumping away from a sharp object or something hot prevents us from being cut or burned. It is only after we have jumped away that we become aware of a our actions (Baines 1998). Unlike other sensations, the perceptive sensation of pain can be influenced by other past or present experiences, for example, heightened pain perception accompanying fear of needles, or lowered pain perception in an injured athlete during a competitive event (Sherwood, 1995).
             There are three categories of pain receptors: 1) Mechanical nociceptors which respond to mechanical damage such as pinching or cutting. 2) Thermal nociceptors which respond to temperature extremes. 3) Polymodal nociceptors which respond equally to all kinds of damaging stimuli (Sherwood, 1995). These nociceptors do not have specialized receptor structures, they are all naked nerve endings. Due to their value in survival nociceptors do not adapt to sustained or repetitive stimulation. The terminals of the afferent fibers synapse with specific interneurons in the spinal cord from which the signal is transmitted to the brain for perceptual processing. One of the neurotransmitters released from this afferent terminals is substance P which is believed to be unique to pain fibers. All nociceptors can be sensitized by the presence of prostaglandin's ,which greatly enhance the receptor response to noxious stimuli, in other words it hurts more when prostaglandin's are present. Prosta!.
             glandin's are a special group of fatty acids derivatives that act locally on being released. Drugs such as aspirin inhibit the synthesis of prostaglandin's, accounting for the pain relieving properties of such drugs (Sherwood, 1995).


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