Most visceral organs, including the heart and blood vessels, are controlled involuntarily by the autonomic nervous system.
The Autonomic Nervous System is one of the two primary components of the peripheral nervous system, which controls the heart, stomach, liver, bladder, intestine, kidneys, lungs, and digestive glands, among other internal organs.
The nervous system is divided into two subsystems: the sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS) (PNS).
When the autonomic nervous system (ANS) gets information about the external environment, it responds either through the sympathetic nervous system (stimulating body activities) or the parasympathetic nervous system (suppressing body functions) (by inhibiting the body processes).