That same dispersion of forces continues once pain messages reach the central nervous system. Suppose you touch a hot stove. Some incoming pain signals are immediately routed to nerve cells that signal muscles to contract, so you pull your hand back. That streamlined pathway is a reflex, one of many protective circuits wired into your nervous system at birth.

Meanwhile the message informing you that you've touched the stove travels along other pathways to higher centers in the brain. One path is an express route that reports the facts: where it hurts; how bad it is; whether the pain is sharp or burning. Other pain pathways plod along more slowly, the nerve fibers branching to make connections with many nerve cells (neurons) en route. Scientists think that these more meandering pathways act as warning systems alerting you of impending damage and in other ways filling out the pain picture. All the pathways combined contribute to the emotional impact of pain -- whether you feel frightened, anxious, angry, annoyed. Experts called those feelings the "suffering" component of pain.

Still other branches of the pain news network are alerting another major division of the nervous system, the autonomic nervous system. That division handles the body's vital functions like breathing, blood flow, pulse rate, digestion, elimination. Pain can sound a general alarm in that system, causing you to sweat or stop digesting your food, increasing your pulse rate and blood pressure, dilating the pupils of your eye, and signaling the release of hormones like epinephrine (adrenaline). Epinephrine aids and abets all those responses as well as triggering the release of sugar stored in the liver to provide an extra boost of energy in an emergency.

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