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Of all the components of the injury response, none is less consistent or less understood than an individual's response to pain. The perception of pain is a primal property of the nervous system and inherent to all people. Pain is more than a sensation. It is an "experience" involving the interaction thoughts, emotions, and past experiences leading to sensory and motor responses.61 Acute pain is the primary reason people seek medical attention and the major complaint that they describe on initial evaluation. Chronic pain may be more debilitating than the trauma itself and may become emotionally and physically debilitating.62,63

• The expression "I have pain" is often uttered and is the main reason people seek medical attention. The term and concept of "Pain" has been defined by the International Association for the Study of Pain as "an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage."64

While humans have experienced pain since the beginning, our understanding of pain remains lacking. This is due to the complex interaction of the many factors that can affect pain. Our understanding of pain as it is defined today is less than 50 years old. In addition to the physiological component, pain also has psychological, emotional, and behavioral components.65 It is described as an individual, highly variable experience and is affected by mood, culture, and past experiences as well as by age and personality.66 What one individual interprets as pain may not be the same for another person in the identical situation.

✱ Practical Evidence

Rather than just being a sensation, pain is a process that involves sensory, motor, and emotional responses. Pain is formally defined as:

an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage. Each individual learns the application of the word through experience related to injury in early life. It is unquestionably a sensation in a part of the body but is also always an emotional experience.64,67

By definition, acute pain is unpleasant and has an identifiable cause and a limited duration.61

Pain, referred to as the fifth vital sign, serves as the body's line of self-defense.68 It warns us that our tissues are in immediate jeopardy or have already been damaged. Pain, caused by mechanical forces or inflammatory mediators, activates protective reflexes and motivates behaviors that help to avoid—or at least decrease—physical trauma. Although we may not like pain, it is crucial to our survival. Loss of pain sensation leaves the body, or a body area, unprotected against serious damage and, potentially, unaware that trauma has occurred.69 Pain loses its value when its defensive meaning is no longer needed. In this case pain may become more debilitating than the actual pathology and becomes a problem in ...

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