Our body has many nerves that come out of our spinal cord and perform various functions, from controlling our muscles to carrying pain sensations. There are twelve nerves that emerge directly from our brain and brain stem. These are called the cranial nerves, and they are intimately involved with multiple areas of our brain which not only control motor action and sensation, but also things like eyesight, hearing, and gland functions. Most of these nerves do not extend below the neck and only a couple travel down into the chest cavity. However, one of them makes its way all the way into the abdominal cavity. This is the 10th cranial nerve, known as the vagus nerve. If you have heard the words vague and vagabond, you know the root word of vagus, which means “wandering.” It is vague and unpredictable in its multiple actions and wandering in nature, starting from the brain stem and then ending up in all sorts of areas in the abdominal cavity. I sometimes imagine the early Greeks like Erasistratus hunched over the human cadaver trying to trace this nerve, which seems to go on and on, and shaking their wise white bearded heads in consternation at not being able to track it fully.
Did you know that the vagus nerve helps with satiety? It is also one of the nerves responsible for throwing out toxins that we might have eaten in spoiled food, through vomiting. And it allows food to move down our gut for absorption and excretion. It is responsible for the gag reflex, so water does not go down into our lungs. And the vagus nerve is involved when you are cleaning your ears of the wax and you feel like coughing. Or why some people faint when the gynecologist is performing a procedure on the cervix before prescribing birth control pills. The effect that it has on our parasympathetic nervous system, however, is one of the most important functions. If you recall, the sympathetic nervous system in our body is related to fight or flight reactions. For example, when we are out on a walk and get confronted by a bear, our sympathetic nervous system sends us running in order to escape the bear. By contrast, the parasympathetic nervous system is related to “rest and digest.” For example, after having a delicious meal and resting, our parasympathetic system reigns. It controls our heart, and our stomach as a result. That is why when there is no danger near, our heart slows down, all the digestive juices are released, and our gut becomes active. Besides the involvement of our heart and our stomach, our emotions are also different when we have a bear running after us versus when we are resting after a home cooked meal.
This is where the role of vagus nerve intersects with Psychiatry . Psychiatrists became interested in how some seizures can be eliminated by stimulating the vagal nerve. They also saw that some people whose seizures got better were also in a better mood. So they created a vagal nerve stimulator to treat depression which is non-responsive to medications. Currently the data is mixed about how effective it can be for depression, though the FDA has approved it. The procedure involves surgery in which an electrical stimulator is implanted to stimulate the vagus nerve in the neck. So while it is an extensive undertaking, it is sometimes worth it.
Our ancestors have known the importance of the vagus nerve and its involvement in emotions for a long time. While they may not have known the anatomical and physiological details, they figured out how to influence the vagus nerve without stimulators. For example, the practice of breathing is all about the vagus nerve. Various pranayamas (yogic breath control techniques) utilize diaphragmatic movements that stimulate part of the vagus nerve that passes through the diaphragm. The same pranayamas change the flow patterns of blood in the chest cavity and heart, creating changes in heartbeat, heart rate variability, and core temperature.
The wandering nerve also has an intimate relationship with the heart. The parasympathetic nervous system acts as a set of brakes for the heart. For example, when we exercise, the sympathetic nervous system speeds up our heart in response to the need for oxygen by the muscles. This is like the accelerator of a car. The more we exercise, the harder we pump on the figurative gas pedal. Our heart would probably speed up and jump out of our chests, were it not for the breaks that keep it from speeding itself into oblivion. These breaks are the parasympathetic nervous system. In a way, the more we exercise, the more our this system gets exercised, which is referred to as the parasympathetic tone of the heart. The changes in our heart rate during anxiety are a little bit similar to exercising in the fact that our heart speeds up. It thinks that there is a bear out there that we need to be prepared for. In fact, it is a commonly observed clinical phenomenon that anxiety causes the heart to speed up, but the reverse is also true. A fast beating heart also increases anxiety independently. In the heart the vagus nerve acts on parasympathetic receptors and through that slows or speeds the transmission of electricity in the electric tracts of the heart.
Similarly, In Traditional Chinese Medicine the heart is often referred to as the seat for Shen, or consciousness. Often conditions like anxiety, mania, difficulty with arousal levels, and sometimes even psychosis are attributed to a disturbance in Shen. The wandering nerve influences Shen. Thus it seems fitting that a classic TCM formula, Xiao Yao Wan, consisting of herbs like White Peony, Bupleurum, Poria, deals with emotional problems and is translated as “Free and easy wanderer.”
The next time you have a gut feeling, be assured that your vagus nerve is telling your brain what your stomach is feeling. That is why gut health plays such an intimate role in emotions. If the enteric nervous system is happy, so is the central nervous system. The bacteria in our gut communicate with the brain through the vagus nerve. Some people theorize that all the dysbiosis and inflammation in the gut is passed on to the brain in this way. That is why some people feel that if you have a “leaky gut,” you are bound to have a “leaky brain.”
There has also been interest in how the vagus nerve can affect the immune system. You might have observed how after a period of stress, a lot of people have a tendency to fall sick. It is because stress can affect multiple areas of our body that have an end result of a weakened immune system. For example stress can cause prolonged high levels of cortisol, the stress hormone in our body. Stress can also decrease the activity of cell that guard our body from invaders like viruses. Similarly stress and inflammation can cause problems with mental health. The vagus nerve is directly involved in modulating the levels of cytokines, the chemicals released during inflammation. So does that mean that adequate breathing can affect immunity? No wonder Ibn-e-Sina, in the healing tradition of Tibb, listed quality of breathing and air as one of the factors involved in disease pathogenesis.
Since the vagus nerve does so many things, vagotomy has multi systemic affects which are fairly deleterious to health. Vagotomy here means that the vagus nerve does not function. We only have to see the rampant problems in our society to see what the effects of a vagotomy might be. We live in a fast paced world, where stress abounds and the fast heart rate struggles to keep us running from the monster outside and the monster inside. It is also no wonder that we are frozen in place with terror, unable to wander anymore, answerable to the production of our factories. Our vagus nerve swings on a pendulum as it tries to adjust to the back and forth of our unpredictable schedules. And we throw challenge after challenge to it, in our quest to seek novel ways of getting thrilled. Our immune systems are poor, we get sick more often. We treat ourselves with antibiotics and kill the bad bacteria while also killing the good bacteria in our guts And so we survive but as lesser people than before for having a killed a part of us to survive. Our vagus deserves better.
However, things are not so doom and gloom. Whereas our current society has many deleterious effects, it also has given us scientific knowledge. Scientific knowledge, however, is a young child. Like the vagus nerve stimulator, the jury is still out whether it does more harm or more good. But we can take the good from it and combine it with the age-old wisdom that is our heritage. We can try to heal ourselves by integrating ourselves with our forefathers. Simple things help exercise our vagus, such as meditation, exercise, breathing more fully, laughing more fully, and having heart-based connections with living beings around us, whether they are people, animals, trees, or mountains. It is beneficial to wander our world as a guest, rather than as a master. The wanderer inside us is the peaceful, receptive, yin side of creation. So the next time you are stressed, think about how you can be more accepting of the circumstances. Use breath, gratitude, and mindfulness and you shall make your vagus and yourself happy.
