PAIN

a complex experience consisting of a physiological (bodily) response to a noxious stimulus followed by an affective (emotional) response to that event. Pain is a warning mechanism that helps to protect an organism by influencing it to withdraw from harmful stimuli; it is primarily associated with injury, or the threat of injury, to bodily tissues. Because it has an affective as well as a sensory component, pain is subjective and difficult to quantify. Although the neuroanatomic basis for pain reception develops in the fetus, individual pain responses are learned in early childhood and are affected by social, cultural, psychological, cognitive, and genetic factors, among others. This accounts for the apparent difference in pain tolerance among people. Athletes may be able to withstand or ignore pain while engaged in a sport, and certain religious practices require participants to endure pain that seems intolerable to most people. The perception of pain may be exacerbated by nonphysical factors such as anxiety, and some pain has no physical cause whatsoever. An important function of pain is to alert the body to potential damage (nociception). The pain sensation, however, is only one part of the nociceptive response, which can include a rise in blood pressure, an increase in heart rate, and a reflexive withdrawal from the noxious stimulus. Acute pain can arise from breaking a bone or touching a hot surface. Two phases are perceived in acute pain: an immediate, intense feeling of short duration, sometimes described as a sharp, pricking sensation, followed by a dull, throbbing sensation. Chronic pain, which is often associated with pathological conditions such as cancer or arthritis, is more difficult to locate and treat. If pain cannot be alleviated, psychological factors such as depression and anxiety can intensify the condition, complicating an already challenging treatment situation.