What does the Autonomic Nervous System (ANS) primarily control?

The Autonomic Nervous System (ANS) is responsible for controlling involuntary bodily functions that are crucial for maintaining homeostasis. Primarily, it governs cardiac and smooth muscle activity, which includes the heart's contractions and the involuntary movements of organs in the digestive system, blood vessels, and internal organs. This system operates automatically, meaning it does not require conscious thought or effort, allowing the body to regulate vital functions without direct input from the brain.

While options related to voluntary muscle movement are under the control of the somatic nervous system, the respiratory rate does involve some voluntary control, particularly during activities like speaking or singing, and is regulated largely by sympathetic and parasympathetic inputs. Digestive enzymes are related to the digestive process and regulated by both the ANS and hormonal signals but are not primarily controlled by the ANS in the way that muscle contractions are. Therefore, the most accurate choice regarding what the ANS primarily controls is the activity of cardiac and smooth muscle.