The process of digesting your last snack or meal or the unconscious regulation of your breathing are all primarily rooted in the nervous system.

Autonomic

Explanation:

ANS or Autonomic nervous system is a part of the peripheral system that controls internal organs. This system works unconsciously and manages bodily functions such as digestion, urination, respiratory rate, heart rate.

This method is the primary mechanism for the regulation of the fight-or-flight response. The autonomic nervous system is controlled by the hypothalamus within the brain.