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The Vagus Nerve



Why are some people more resilient to stress than others? And what role does the vagus nerve play in this process?

Ever wondered why some people float through life, dealing with one challenging situation after another, while others get thrown off balance by even small things?

Ever wondered why your own nervous system seems to have less stamina and resilience in the face of adversity?

The answer, in part, lies in the resilience of your vagus nerve. The vagus nerve is one of the largest nerves in the body. It acts as the body's superhighway, carrying information between the brain, the gut, and the organs. Importantly, the vagus nerve is a major player in controlling the body’s response to stress. It helps regulate the parasympathetic response and put us into a more calm, rest and digest response. But did you know that not all vagus nerves are the same? That is one of the major reasons why some people are more resilient and relax faster after stress. So why do some people have stronger vagus activity?

One main reason lies in your genes.

But, there’s good news. We now know that there are many ways to influence these genes and strengthen vagus nerve activity. We can do so by incorporating certain yoga techniques and habits into our lives to help strengthen our nervous system.

The Automatic Nervous System (ANS) is a complex biological system which allows us to survive by regulating the functions of our internal organs such as the heart, lungs, stomach and intestines. Most of this is done outside of our conscious awareness.

Most of our feelings (both physical and emotional) have their origin in the body. That is, the state of our body and its functions drive the state of our emotions and our emotions also affect our body. Traditionally thought of as having two divisions, sympathetic (fight or flight) and parasympathetic (rest and digest) a newer understanding of how the autonomic nervous system functions has been informed by the Polyvagal Theory. The vagus nerve is an intrinsic component of the ANS and it communicates an extensive range of signals about our state bidirectionally (from the brain to the body and the body to the brain).

The 3 neural circuits of the ANS are:


1: Social Engagement System

(Important for healthy engagement with the world). The SES interprets cues from our environment like vocal prosody, eye contact, and facial gestures to gauge our level of safety. When the brain/body appraises the environment as safe, defensive responses are inhibited and a calm state emerges. Your heart rate slows, your muscles relax and your breathing becomes more regulated. You can see this in your face and hear it in your voice. When you feel this way, you can rest, digest, control your emotions and thinking. You can learn, and you can be social. The SES is governed by the ventral vagal complex and is myelinated (making transmission of information smoother and faster).

2: Immobilisation.

If we detect a life threat, our response may devolve to immobilisation, or freezing behavior. This would engage a more primitive branch of the vagus nerve (the dorsal vagal complex). The result is a system shutdown that causes fainting, immobilisation, or dissociation.

3: Mobilisation.

When the brain/body perceives a threat, the SES will release the vagal brake to engage the sympathetic system instantaneously in order to support defense rather than health. When this happens, you feel your heart rate increase, your face flush and your palms sweat. Your breathing increases and your body prepares to fight or flee. In this situation, you have no time to think things through rationally and no capacity to be social.

The three different circuits above provide the neural regulation of autonomic state (vagal tone). This is not an on/off system; it is a dynamic and fluid interaction. We are constantly adjusting our physiological state to meet the world and our perceptions about it. Sometimes, however, our autonomic state can get stuck in one of these neural circuits. An example is anxiety wherein one is more prone to sympathetic arousal (mobilisation) and has less access to the other autonomic states.

Good vagal tone promotes homeostasis of the ANS. High vagal tone improves your ability to flexibly shift in and out of different states based on the situation. Low vagal tone is associated with a reduced capacity to respond to stressors appropriately.