Parasympathetic nervous system

The Parasympathetic nervous system (PNS or PSNS) affects the heart, lungs, eyes, digestive system and blood vessels. It does the opposite of the sympathetic nervous system and the two nervous systems balance each other's effects. While the sympathetic nervous system has "fight or flight" responses, the Parasympathetic nervous system lets the person "rest and digest". Note: There is little information on the Parasympathetic nervous system to reference and Wikipedia is often referenced by other articles/sites as it has comprehensive yet easily understood information on its nervous system responsibility.