that portion of the autonomic nervous system (also called the parasympathetic system) which produces involuntary responses from the body such as dilation of the blood vessels, an increasing of the activity of the digestive and reproductive organs and glands, contraction of the pupils of the eyes, slowing down of the heart beat, and many others. See also autonomic in this glossary.—Science of Survival Glossary (app 11.7.90)