Vagal Tone

The vagus nerve is cranial nerve number ten. It is one of twelve nerves that arise from your brain. Although this vagus is different than the Vegas in Nevada, the activity level of this nerve is involved in so many processes that it is just as wild. Now you might be thinking, “Okay so what does this crazy vagus nerve actually do?” This nerve is the longest of the cranial nerves. It connects to your heart, blood vessels, lungs, esophagus, stomach, and intestines. It carries both sensory and motor fibers for communication between the brain and body, and it is a crucial part of the parasympathetic nervous system.

Angela Nguyen

Angela Nguyen

The body is constantly trying to find the balance between the sympathetic and parasympathetic nervous system. The sympathetic system is activated when our bodies are under a lot of stress. It prepares our bodies to face stress or run from it by increasing our heart rate, increasing respiration, and decreasing gastrointestinal motility. On the other hand, the parasympathetic system has the opposite effect – slowing our heart rate and increasing digestion. This is largely controlled by vagal tone. The vagus nerve is closely tied to the heart. It innervates the sinus node in the right atrium of the heart, meaning that it is responsible for controlling heart rate. This allows the vagus nerve to have a strong impact on heart rate variability (HRV).

HRV is not only a measure of vagus nerve function, but of bodily health as well. “High level of HRV is associated with good health and well-being and good resilience in emotional self-regulation”.1 Decreased HRV is associated with a low vagal tone. It has been said that this low vagal tone can be associated with increased inflammation. The vagus nerve is involved with almost every organ in your body, and it sends sensory information from these organs back to your brain. When the vagus nerve detects inflammation, it can tell the brain to release anti-inflammatory neurotransmitters to respond. Low vagal tone has been associated with increased C reactive protein, IL-6, and tumor necrosis factor (TNF), which are all inflammatory markers. Under normal conditions, inflammation can be an important part of the healing process. However, sustained or chronic inflammation can be detrimental to your health. Having proper vagal tone can help keep inflammation under control.

What’s exciting is that vagal tone is being further explored to see how stimulation of this nerve can be used to treat a variety of conditions. For example, scientists are experimenting with vagus nerve stimulation to treat conditions caused by inflammation such as rheumatoid arthritis.   tested this hypothesis on rats with good results. He moved his experiment over to human subjects and found that, “the creation of implants to stimulate the vagus nerve via electronic implants showed a drastic reduction, and even remission, in rheumatoid arthritis…hemorrhagic shock, and other equally serious inflammatory syndromes.”2

Another area of research is being done to see the effects of vagal stimulation on depression. Depression is a major mental health condition, and it is often treated with pharmaceuticals. Over the course of one year of treatment, the response rate increased to 53%.3 This was only one study, but the results encourage further research in this field.


  1. Breit, S., Kupferberg, A., Rogler, G., & Hasler, G. (2018). Vagus Nerve as Modulator of the Brain–Gut Axis in Psychiatric and Inflammatory Disorders. Frontiers in Psychiatry9. doi: 10.3389/fpsyt.2018.00044
  2. Rosenfeld, J. (2018, November 13). 9 Fascinating Facts About the Vagus Nerve. Retrieved from
  3. Bonaz, B., Sinniger, V., & Pellissier, S. (2016). Vagal tone: effects on sensitivity, motility, and inflammation. Neurogastroenterology & Motility28(4), 455–462. doi: 10.1111/nmo.12817


This article first appeared in the May 2020 issue of Lifelines, the Life West student magazine.

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