Acupuncture head. Cast of the head of a Chinese man showing a traditional acupuncture chart. Meridians (lines) and points are mapped out across the skin surface (the meridians relate to channels of energy within the body). Imbalances in the flow of energy are thought to cause pain and disease. The insertion of needles at precise points (marked by dots) at different angles, temperatures and speeds according to the disorder, is thought to stimulate energy flow and may alleviate the problem. Acupuncture may work by inducing the production of endorphins (natural analgesics) within the central nervous system, or by stimulat- ing the nerves which inhibits the original pain.