Parasympathetic Nervous System
A subdivision of the autonomic nervous system regulating largely involuntary internal processes, focused on energy storage, growth & restoration (slows heart beat, stimulate digestion). Inhibits and opposes the sympathetic nervous system subdivision.
Bear, M.F., Connors, B.W. & Paradiso, M.A. (2001). Neuroscience: Exploring the Brain. (2nd Edition). Baltimore, MD: Lippincott Williams & Wilkins.