Sympathetic and Parasympathetic nerves are part of
The autonomic nervous system also has two divisions: the sympathetic division and the parasympathetic division. These two divisions have opposing effects on the internal organs. The sympathetic nervous system prepares the body for intense physical activity and is often referred to as the fight-or-flight response. The parasympathetic nervous system has almost the exact opposite effect and relaxes the body and inhibits or slows many high energy functions.