What aspect of digestion does the autonomic nervous system NOT regulate?

The autonomic nervous system (ANS) plays a crucial role in regulating various involuntary processes in the body, including many functions related to digestion. Options A, B, and D all pertain to digestive functions that the ANS directly influences. Salivation involves stimulating the salivary glands, which is supported by the parasympathetic branch of the ANS. Peristalsis is the wave-like muscle contractions that move food through the digestive tract, also regulated by the ANS to ensure proper movement and coordination. Additionally, the secretion of digestive enzymes is controlled by the ANS to assist in the breakdown of food within the gastrointestinal tract.

In contrast, controlled breathing primarily involves the somatic nervous system, which is responsible for voluntary movements and is more associated with consciously managing the respiratory muscles. While there may be some influence from the ANS during certain conditions (like during rest), it does not play a primary role in the conscious control of breathing compared to its significant influence on the actions related to digestion. Thus, the correct response highlights that controlled breathing is not regulated by the autonomic nervous system like the other listed processes.