Your brain is actually the centre of a vast network of nerves - a complex system that extends throughout your body. Scientists refer to the brain and the spinal cord as the central nervous system and everything else as the peripheral nervous system.
The peripheral nervous system is a bi-directional information highway, sending information from bodily organs to the brain and operational instructions from the brain back to the body.
Some nerves carry information from our sensory organs -- such as our eyes, ears and skin. These help the brain to build a detailed perceptual picture of the world around us. Scientists call this exteroception.
But we also have an often overlooked set of nerves which deal with interoception -- the sensing of the internal state of the body. Some of this perception of bodily state (such as pain) is just as clear and sharp as the sensations of the outside word. But we also receive interoceptive nerve signals from our visceral (internal) organs which tends to be less sharp but in no way less important. Probably the most important interoceptive nerve in our body is the vagus nerve which connects all of these visceral organs to the brain.
The sensations we receive along the vagus nerve tell the brain about the state of these organs; and signals from the brain control the function of these organs - everything from the beating of your heart to the digestion of food in your stomach and intestines to the filtering of blood through your liver.
The vagus nerve forms a major part of half of the interoceptive nervous system called the parasympathetic nervous system. The other half is called the sympathetic nervous system. These two halves work together to maintain bodily homeostasis -- which refers to the body’s natural equilibrium state.
The sympathetic nervous system speeds up the body and becomes more active during stressful and dangerous situations; while the parasympathetic nervous system relaxes the body and becomes more active when we are in safe situations so that we can effectively regenerate and heal. Homeostasis is the balance between these two forces and is crucial for survival in the short term, and health and well being in the long term.
What we feel from our interoceptive nervous system is often vague compared to our exteroceptive perception. This is actually an important evolutionary adaptation. If our interoceptive perceptions were as loud and vivid as our exteroceptive perceptions, all we would ever hear would be the beating of our hearts, the air rushing into our lungs and the gurgles of our digestive system. These sounds would overwhelm external noises so much that we might not notice that sabre tooth tiger sneaking up on us.
But these sensations are nevertheless very important to survival. So the brain solves this problem by turning the sensations into broad emotions and vague feelings. This filtering can sometimes lead to confusion however -- for example when you get short tempered because you’re hungry.
And so, one of the consequences of this evolutionary adaptation is that when your vagus nerve is reporting a problem or has a problem with its own function, it’s not always easy to know. This uncertainty makes it a challenge to recognise when there might be a problem. Here are a few tips on what to look out for -- but remember, these are just guidelines. If you recognise any of the things below, it doesn’t necessarily mean that it’s caused by an issue with your vagus nerve, it just means you might benefit from trying out a few things.
Vagus nerve health (sometimes referred to as vagal tone) is worth improving even if you don’t experience any of the specific issues below. Like sticking to regular exercise and a healthy diet is good for you even if you don’t feel like anything in particular is wrong.
OK, mood changes can be caused by a lot of things, so just because you experience some, doesn’t mean you have issues with your vagus nerve. But emotions don’t occur in a void and like we said earlier, they are not only caused by external, environmental factors, but by the internal state of your body.
If you’re experiencing unusual and persistent mood swings, it could be a sign you have some underlying health issues.
The vagus nerve connects to all your visceral organs, so if the integrity of the vagus nerve declines, it hinders communication between the brain and these organs. This can be caused by and cause degrees of dysfunction in your organs. Early stages of this affects mood because, in a way, you feel that something is not quite right. So you may have inexplicable feelings of anxiety, sadness, tension, bouts of anger or general feelings of discomfort.
In some cases, it has been shown that dysfunction of the vagus nerve can also affect memory and cognition. Scientists still don’t fully understand the mechanisms, but studies have found solid links between good vagal tone and good mental health.
A lack of energy, feeling of weakness or fatigue, dizziness or fainting can all be signs that your heart and circulatory systems (the blood vessels) are not responding well to the oxygen and energy demands that are being placed on them. Our hearts actually respond from beat to beat to changes in the needs of the brain and body; and blood vessels expand and contract to regulate blood pressure. How well your heart adapts can be measured by your heart rate variability (HRV). You can learn more about this by reading our earlier post.
Experts are increasingly using HRV as a better measure of health and fitness than a simplistic average heart rate. A low HRV can be indicative of a number of underlying health issues.
As heart rate is highly regulated by the vagus nerve, it is one of the most useful indicators of vagal tone. Improving your HRV using diet and exercise or vagus nerve stimulation is one of the best things you can do for your long term health.
Your guts are like a second brain, containing more than 100 million neurons (or brain cells). Signals from these cells are often the drivers of the mood changes we mentioned earlier.
The vagus nerve is the main link between your digestive system and your brain. Signalling from the brain along the vagus nerve coordinates the digestive process and dysfunction in the nerve hinders communication. This can lead to an array of problems such as frequent indigestion, slow emptying of the stomach, heartburn, irritable bowels or weight gain.
Inflammation is part of your body’s natural response to injury or infection. This is highly controlled by brain signalling along the nervous system and the vagus nerve is one of the primary pathways which signal to the brain the need for an inflammatory response.
The bi-directional communication both triggers the start of an inflammatory response and regulates the amount of inflammation that occurs. However when these neural circuits perform ineffectively, this can lead to excess inflammation. This in turn can lead to diseases such as arthritis and in extreme cases, as we have seen recently in the immune response to coronavirus infections, uncontrolled inflammation can become life threatening.
Studies show that stimulation of the vagus nerve can ease the suffering of arthritis and may help improve immune system health.
The body’s inflammatory response has been highlighted by a number of recent scientific and government reports as a primary driver in age related decline in health.
The vagus nerve plays an important role in the swallowing process. Although we take swallowing very much for granted, it requires a complex series of coordinated actions.
As you swallow a number of reflex actions occur which shut the nasal cavities and open the oral cavities, followed by esophageal contractions which push down into the stomach. The vagus nerve plays an important motor and sensory role in this process, working in concert with a number of other cranial nerves.
Dysfunction in the vagus nerve can make swallowing difficult and even dangerous. A small mistake can result in food passing into your lungs rather than your stomach. If this happens, impulses from the vagus nerve induce reflexive coughing to try to expel the food or drink from the lungs.
If you recognise any of the above issues, you may find great benefit from vagus nerve stimulation. Severe or sudden cases should always be discussed with a medical practitioner, but we all sometimes experience these changes to a greater or lesser degree. If they are mild but noticeable, simple lifestyle changes can help.
At vagus.net, we believe that electrical vagus nerve stimulation can help support these lifestyle changes. A growing body of recent science is showing that electrical treatments (sometimes called eletroceuticals) can in many cases be more effective than pharmaceutical interventions and carry almost no side-effects. However, electrical nerve stimulation shouldn’t be seen as a panacea. It shouldn’t be the only thing you do and it often works best when it’s used in conjunction with other lifestyle changes.
Improving vagal tone using direct electrical stimulation can often make it easier to engage in other activities, such as regular exercise and healthy sleep patterns, which in turn help strengthen vagal tone, leading to a virtuous cycle of better health.
Stay tuned for tips about other things you can incorporate into your life to improve vagus nerve health.