Autonomous or visceral nervous system. The system does not consult the will of the individual. It works on its own inputs. Autonomous nervous system consists of only motor nerve fibres that innervate all organs and glands of the body. Depending upon the input, autonomous nervous system stimulates, slows down or stops the activity of an organ. For its working, autonomous or visceral nervous system has two components, sympathetic and parasympathetic. Sympathetic nervous system originates from thoracico-lumbar region, forms two ganglionic chains which send out long nerve fibres to various organs. The sympathetic nerve fibres activate the organs by release of nor-adrenaline. Parasympathetic nervous system is called cranio-sacral as it originates from some cranial and sacral nerves. It has long preganglionic fibres and ganglia attached to organs that are innervated. Its post ganglionic fibres secrete acetylcholine into organs for moderating or reducing their activity.