Unlike the sin city many people in our society have grown a love/hate relationship with, what happens in the vagus nerve, shouldn't stay there. Author/Osteopath/Craniosacral therapist Stanley Rosenberg very clearly explains it's importance in his book Accessing the Healing Power of the Vagus Nerve.
A lot of attention has been brought to the vagus nerve in the world of health with Dr. Stephen Porges The Polyvagal Theory, who writes a forward in the book. Dr. Porges really emphasized it's importance in regards to the relationship of the heart-rate, facial muscles, and one's ability to recognize safe or dangerous situations, among other points and studies. Porges gained the attention of people in the field of yoga, meditation, and general new age as it helped people understand these states of relaxation, clarity, and health they were achieving without much of a scientific explanation as to why. Porges described the relationship between the heart, facial muscles, brain, and the vagus nerve as they work together in harmony for parasympathetic activity when one strives for ideal health and peace of mind.
However, The Polyvagal Theory is by no means an easy read, nor is it written in laymen's terms. It also seems to have been written for people working in the world of academia, medicine, and science. Conversely, Rosenberg's Accessing the Healing Power of the Vagus Nerve lays everything out very simply for anyone interested in understanding this physiological phenomenon, regardless of their backgrounds.
So lets take a look at the vagus nerve. The vagus nerve stretches all the way from our head to the bottom of our torso and it connects with most of our visceral organs. It stimulates 75% of our parasympathetic response (rest and digest) in our autonomic nervous system. This affects our bodies ability to heal tremendously as it keeps things our muscles relaxed, healthy blood circulation, unrestricted air passage, etc.
Conversely, our sympathetic nervous system is what stimulates our fight/flight response (dilated pupils, stimulated adrenal glands, restricted blood flow, etc) when we perceive something as a threat. All mammals have this function as it's what protects and enables them to survive in the wild upon encountering predators or prey. In the modern era, an angry boss or a missed train may be perceived by many as a threat as well. Which one of these two states do you think your average working American spends most of his/her time in?
I quite often have to explain this to my clients as craniosacral therapy works by bringing people into a parasympathetic state in order to balance the nervous system. Also, working with the vagus nerve helps with autoimmune disorders and inflammatory issues. I guess if everyone could easily access the vagus nerve, myself and my colleagues might be out of a job!
Rosenberg might be on the way to helping make that happen though as he also has a few exercises one can do for bringing people into a parasympathetic state and working with undesirable patterns in the autonomic nervous system. One of the books I recommend for understanding how we're wired and an interesting read at that.