Sympathetic nerves in the upper body. Historical anatomical artwork of a side view of a dissected human face, neck and chest, showing the origin and route of parts of the sympathetic nervous system. This system is responsible for triggering energy production by the body, especially in emergency situations. Nerves (white) are seen branching out across the body from ganglions near the spine (down left). One function is the ennervation of the heart (lower centre). Sympathetic nerves arise from white matter in the spinal cord, unlike the nerves under conscious control that arise from the grey matter. Artwork from The Nerves of the Human Body (Ed. Jones Quain, London, 1839).