The autonomic nervous system (ANS) innervates the heart, smooth muscles, glands and viscera and is divided into the parasympathetic and sympathetic nervous systems. The parasympathetic system participates in tissue building and the sympathetic system enables responses to stress. Both systems have efferent neurons that travel from the CNS to effector organs via a two-neuron chain, with preganglionic neurons synapsing in ganglia and postganglionic neurons innervating the organs. The sympathetic system originates in the thoracic and lumbar spinal cord and parasympathetic system originates in the cranial and sacral regions. The sympathetic system prepares the body for fight or flight while the parasympathetic