Most of the major muscle groups used or movement and communication are voluntary. Involuntary muscles would be things like your heart and the muscles around your intestines, which you generally cannot consciously control. The skeletal is called voluntary muscle because it is usually subject to conscious control.
Medical Definition of Autonomic nervous system. Autonomic nervous system: A part of the nervous system that regulates key involuntary functions of the body, including the activity of the heart muscle; the smooth muscles, including the muscles of the intestinal tract; and the glands.
Noun. 1. ANS-the part of the nervous system of vertebrates that controls involuntary actions of the smooth muscles and heart and glands. autonomic nervous system. autonomic ganglion-any of the ganglia of the autonomic system whose unmyelinated fibers innervate the internal organs.