It controls the secretion of some hormones.
The parasympathetic system brings the body back to a state of equilibrium. It slows heart rate and decreases the release of hormones into the blood stream. The activity of the parasympathetic system causes more localized reactions than does the sympathetic system as much of its output is to specific organs.
The sympathetic system prepares the body for fight or flight reactions. Action of this system results in accelerated heart rate, increased blood pressure and blood flow away from the digestive system toward the brain, heart and skeletal muscles. It also causes adrenaline to be released, temporarily increasing physical strength. SYPATHETIC NERVES
It is a nice, sunny day...you are taking a nice walk in the park. Suddenly, a rhino appears in your path. Do you stay and fight OR do you turn and run away? These are "Fight or Flight" responses. In these types of situations, your sympathetic nervous system is called into action - it uses energy - your blood pressure increases, your heart beats faster, and digestion slows down.