The autonomic nervous system is part of the Peripheral Nervous System, or PNS. The autonomic nervous system is responsible for involuntary movements, the smooth and cardiac m … uscles. Sympathetic (fight or flight) and Parasympathetic (rest and digest) are branches of the ANS.he autonomic nervous system is a division of the peripheral nervous system that controls automatic responses in the body, such as the heart rate, hormone levels, gastrointest … inal functions, and metabolism.