The autonomic nervous system is further divided into sympathetic and parasympathetic systems. The sympathetic is the part that responds when the body needs sudden actions—what is generally referred to as the fight-or-flight response. The parasympathetic is sometimes referred to as the “rest and digest” or “feed and breed” system and looks after a miscellany of other, generally less urgent matters like digestion and waste disposal, the production of saliva and tears, and sexual arousal (which may be intense but not urgent in the fight-or-flight sense).
