the portions of the central and peripheral nervous systems involved primarily in involuntary bodily functions, for example, circulatory, digestive, and respiratory organs. Both the central and peripheral systems contain autonomic nerves and autonomic ganglia. Autonomic responses typically involve some changes in smooth-muscle or glandular activity. Symptoms include changes in heart rate, salivation, digestion, perspiration, secretion of hormones from the adrenal medulla, bladder contraction, and engorgement of the penis and clitoris. The system is called autonomic because it was once thought to function completely independently from the central nervous system.