The vagus nerve also plays a role in manipulating anxiety levels. Here is an excerpt from Psychology Spot:
"The vagus nerve intervenes in the sensitivity of the respiratory mucous membranes and transmits the rhythm, strength and frequency of breathing. It affects the pharynx, the larynx, the esophagus, the trachea and the bronchi, as well as administering nerve fibers to the heart, stomach, pancreas and liver. But it also carries out the inverse mission; that is, it receives signals from the internal organs and sends them to the brain to be processed.
Although perhaps the most interesting thing is the relationship between the vagus nerve and anxiety as it also transmits signals of nervousness or calm, anger or relaxation." https://psychology-spot.com/vagus-nerve-disorders/
There are also some very technical articles online covering this topic but I liked the simplicity of the Psychology Spot article.