Pain is an unpleasant sensory and emotional experience that is normally
associated with injury or threat of injury to body
tissues. The behavior of a person in pain must be understood as a complex interaction of physiological, psychological, and sociological factors. For example, differences can be observed between individuals and between members of different cultures in their degree of response to injury. In everyday life, acute pain performs a valuable function in minimizing the harm of
accidental injury or minor disease. Persons who are born without the ability to feel pain or who develop such an inability through disease are at great risk of the
consequences of unrecognized injury. On the other hand, the severe pain associated with surgery, accidental injury, or childbirth can trigger reflexes that affect breathing, heart function, and blood pressure, sometimes with serious consequences.
Acute pain may become chronicÑpersisting indefinitely and serving no beneficial purposeÑwhen it is not effectively treated or when healing is incomplete. Such pain is very resistant to medical intervention and may cause prolonged suffering and discouragement.