VAGUS NERVE
Now, if there is one part of the nervous system you want to be friends with, that is Vagus Nerve. The vagus nerve is the longest cranial nerve in the body. The vagus nerve rules the parasympathetic nervous system — rest and digest/also freeze. There are actually two parasympathetic nervous systems - a belly side vagus (rest/digest/calm) and a back side vagus (freeze/reptilian).