Pain

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pain, complex experience consisting of a physiological and a psychological response to a noxious stimulus. Pain is a warning mechanism that protects an organism by influencing it to withdraw from harmful stimuli; it is primarily associated with injury or the threat of injury.

Pain is subjective and difficult to quantify, because it has both an affective and a sensory component. Although the neuroanatomic basis of pain reception develops before birth, individual pain responses are learned in early childhood and are affected by social, cultural, psychological, cognitive, and genetic factors, among others. Those factors account for differences in pain tolerance among humans. Athletes, for example, may be able to withstand or ignore pain while engaged in a sport, and certain religious practices may require participants to endure pain that seems intolerable to most people.

An important function of pain is to alert the body to potential damage. That is accomplished through nociception, the neural processing of harmful stimuli. The pain sensation, however, is only one part of the nociceptive response, which may include an increase 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. During acute pain, an immediate intense feeling of short duration, sometimes described as a sharp pricking sensation, is followed by a dull throbbing sensation. Chronic pain, which is often associated with diseases 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.