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.
Full Text. The autonomic nervous system (ANS) is the part of the peripheral nervous system that controls involuntary functions that are critical for survival. The ANS participates in the regulation of heart rate, digestion, respiratory rate, pupil dilation, and sexual arousal, among other bodily processes.