SLEEP SOUNDLY Our nervous system consists of the Central Nervous System and Peripheral Nervous System.   The Peripheral Nervous System is divided into the somatic, autonomic and enteric nervous systems. The Autonomic Nervous System is subdivided into the Sympathetic and Parasympathetic Nervous Systems. The Sympathetic Nervous System is related to fight-or-flight. When this fight-or-flight system is engaged, bodily functions like digestion slow down, but your blood pressure and heart rate increase. The Parasympathetic Nervous System is associated with relaxation, rest-and-digest, and gives the body a chance to recuperate from the Sympathetic Nervous System activities, and bodily functions like digestion speed up. So what does the nervous system have to do with.