The phrase "autonomic system" refers to a part of our body that controls functions we don't consciously think about, like breathing, digestion, and heart rate. It works automatically, without us having to instruct it consciously. Full definition
«Serotonin is a key neurochemical that plays an important role in the control and management of the complex respiratory, cardiovascular and autonomic systems within the human infant brainstem. (sciencedaily.com)
Autonomic system dysfunction can be reversed if you first trace to the root cause and find out what is the root issues. (drlam.com)
It is the headquarters for the body's autonomic system which regulates such things as respiration and body temperature. (slaw.ca)