The Traditional Chinese Medicine explanation is that channels of energy run in regular patterns up and down the body and over its surface. These energy channels, called meridians, are like rivers flowing through the body to irrigate and nourish the muscles and tissues. An obstruction in the movement of these energy rivers is like a dam that backs up and creates pain or other problems. The acupuncture needles send signals to unblock the obstructions at the dams, and establish the free flow throughout the body, reducing or eliminating pain. Free flow = no pain. The modern scientific explanation is that needling the acupuncture points stimulates the nervous system to release chemicals (such as endorphins and adenosine) in the muscles, spinal cord, and brain. These chemicals will either change the experience of pain, or they will trigger the release of other chemicals and hormones which influence the body's own internal regulating system. The improved energy and biochemical balance produced by acupuncture results in stimulating the body's natural healing abilities, and in promoting physical and emotional well-being.