OUCH! YOU ’VE GOT SOME NERVE! Serious pain starts with the stimulation of one or more of the body ’s many special sensors, called nociceptors , in the skin or internal organs. These special sensors receive information about intense heat, extreme pressure, sharp pricks O「 cuts, or other events that can cause body damage. Two types of nerve fibers carry this information from the nociceptors to the spinal cord: A-delta fibers, which transmit information quickly and appear to be responsible for sudden and sharp feelings of pain; and C-type fibers, which transmit pain impulses more slowly and may be the cause of a nagging sense of pain. At the spinal cord, messages from nociceptors may be modified by other spinal nerves that enhance or, more frequently, diminish the intensity of the pain. The pain impulse then travels to several parts of the brain. Some brain areas determine where the pain is and what is causing it, while other areas combine the sensory information with the total state of the body and produce the emotional sensation called pain. These same brain centers can activate long nerve fibers that descend to the place in the spinal cord where the pain signal originates and decrease the signal. In the mid-1970s, researchers showed that many nerve fibers that holdback pain messages in the spinal cord release a neurotransmitter called enkephalin . Some areas of the brain that process pain messages produce a related chemical called endorphin. Although the exact roles of these two substances in pain perception is not yet clear, scientists hope that studies of these chemicals may eventually give rise to better types of pain treatment. The complex nature of pain is illustrated by the stories of soldiers who are severely wounded and do not complain of pain, or of athletes who are injured but do not experience pain until the contest is over. In some cultures, an operation can be performed on the skull without an anesthetic (anti-pain drug). On the other hand, scientists have recently shown that the expectation of pain can actually intensify the experience, perhaps by inducing anxiety. The emotional component of pain is also illustrated by the words frequently used to describe its nature, such as “vicious” “nauseating” and “nagging”. Acute or severe pain-such as that produced by physical injury , burns or surgery 一 is most often treated with anti-pain drugs, which can range from simple ones, like aspirin, to more powerful drugs, like morphine. In the terminal stages of cancer, combinations of powerful painkilling drugs may be used, including mood-altering drugs, like tranquilizers or anti-depressants. In some patients who have had surgery, pain is effectively relieved by a nerve block: the injection of an anesthetic into the regional nerve center through which the nerves from the surgery site pass. With certain types of back pain, surgery can correct the problem causing the pain. Beginning about 1965, physicians came to appreciate the uniqueness of the condition called "chronic pain. ” In this syndrome (bodily condition). patients may com­ plain of pain for years, without having any apparent or detectable injury or cause. Researchers suggest that chronic pain is a behavior state, initiated by a real injury, in which the pain has lasted so long that it has itself become the disease. Of the many millions of Americans who suffer from chronic pain, one-third have back pain and another third arthritis (swelling between the bone joints). Many of these patients are dependent on strong painkilling medicines, and they usually have fallen into a cycle of pain, depression, and inactivity. A number of special clinics have been formed to treat people who suffer from chronic pain. Such clinics emphasize reduction of drug dosages, along with exercise, activity therapy, and mental relaxation techniques such as hypnosis and biofeedback. Some include psychological counseling, and many attempt to change learned pain behaviors by enlisting the patient ’s family. In other cases, patients are helped by an electronic nerve-stimulating device, called T.E.N.S., that can be used to send electricity into the nerves and up the spinal cord. Exactly how and why this device works is not known, but it may stimulate the brain to send pain-inhibiting impulses down the spine.