What is the autonomic nervous system?

The autonomic nervous system controls the involuntary action of the body. It mainly controls and integrates the functions of internal organs like heart, blood vessels, glands, smooth muscles and uterus in the body. The autonomic nervous system is subdivided into (i) sympathetic and (ii) parasympathetic system. The organs receive nerves from both sympathetic and parasympathetic nerve fibers. They have antagonistic effects on the organs if one is stimulatory, the other is inhibitory.