Pain

Pain, in its most basic form, can be described as an unpleasant physical sensation resulting from a variety of outside stimuli, from a pin prick to a serious burn. However, pain is a complex experience that eludes simple definitions. Not only does the central nervous system play a crucial role in the experience of pain, but psychological factors can also affect how an individual perceives pain. Most pain results from the intense stimulation of nerve endings beneath the skin that serve as the body's alarm system for detecting injury. For the majority of people, such pain is immediate and intense. However, in certain situations, the feeling of pain may be delayed or may fail to occur altogether (as sometimes happens with soldiers in the midst of battle). Another baffling aspect of pain is its persistence after the source of pain is gone, such as phantom limb pain that continues even after the injured limb has been amputated. Although people usually seek to avoid pain, some people, called sadomasochists, can derive pleasure from pain.