by Michael W. Hall, D.C.
From very early in our lives—actually in utero— one of the first reflexes that can be observed is that of withdrawal. Withdrawal is a whole-body reaction that is seen in response to a stimulus that is in some way adverse to the developing fetus, such as touch, noise, a shift in position, or an alarm of some sort. Withdrawal affords protection, removing oneself from harm or danger. Reflexes play an important part of our lives both during early development and as we grow into adults. Reflexes are often classified as primitive (also called equilibrial) and postural.
As the brain develops there is an order to its formation. First the brainstem, or lower brain, develops to encompass our vital centers for breathing, regulating heartbeat and blood pressure, and reflexive movements to begin our orientation to our new world. Once we are born, we spend much of our first year trying to eventually stand on two legs and begin walking on our own. During this first year many of the primitive reflexes are gradually dampened or inhibited by our developing cortex, the newer brain. As we begin to interpret our environment, we make our own impressions about whether stimuli are harmful or helpful to us. During this developmental period, primitive reflexes are extinguished as postural reflexes begin to dominate.
This is when the vagus nerve, an inexplicably complex nerve with functions that we are just starting to recognize and appreciate, enters the picture. Many in the health sciences will have no doubt learned about cranial nerves that primarily emerge from our brainstem to supply nerves to our eyes, ears, nose, and mouth, which let us relate and express ourselves on a daily basis. Most of these nerves are taught and explained by their outgoing function. I’d like to share with you a bit about the vagus nerve from the incoming perspective.
Many scientists consider the vagus to be the nerve which gives a “braking” type innervation to the heart and lungs—in other words, it slows things down. The vagus nerve also innervates our larynx and pharynx for speaking and swallowing, and innervates our gut for digestion. It has been touted as being the longest cranial nerve; there’s a precarious understanding of it being the “wandering” cranial nerve (hence its name: vagus and vagabond have the same Latin root), in that it is composed primarily of afferent nerve fibers, fibers which carry information into the nerve system.
This is where things begin to get interesting. Science has now uncovered that the vagus nerve is really “three” nerves in one, i.e. polyvagal. There is a myelinated (or insulated) portion of the nerve that is above the diaphragm and innervates the heart and lungs. This is often called the “smart” vagus, as it is intimately related to how we see and respond to people and things around us. It helps us differentiate friend from foe, or something beneficial from something harmful. Our heartbeat and breathing rate are also influenced by this portion of the vagus.
The unmyelinated part of the vagus nerve provides the innervation to our gut so it can secrete digestive enzymes and break down our food for nutritional intake. It also detects injury to our stomach lining. When people complain of indigestion or heartburn, they often have a decrease in function or irritability of this aspect of the nerve.
Best of all is the third part of the vagus nerve, what has fondly been referred to as the “social” vagus. This sends information to the central nerve system and our higher centers. While the other two parts primarily send information to our heart, lungs, and gut, this third part of the nerve is concerned with taking information to our higher brain. This function is what helps us to interpret our environment. Are we in a friendly place? Are we comforted and supported by people who genuinely care about us? Can we truly relax and know that we are not in danger?
For example, say you take your children to the park, and while the kids are playing you turn to visit with a friend. When you check on your kids a few moments later, you immediately notice that you can’t see your youngest boy. What is your first thought? Most likely, it’s a negative scenario, one in which the child has been abducted or harmed in some way. This is the start of a physiological response from your brain to engage you to quickly find your kid. Your heart races, your respiration increases, your muscles tighten—your systems are on high alert and nothing will deter you until you find your child. You are in an “alarm” response. This is good for the scenario at hand, and necessary. Now, after you call your son’s name, you see him come from behind a bush carrying a tennis ball that he found. All is suddenly well. Your child is safe, and your system begins the process of coming out of the “alarm” state. Gradually, your heart rate and breathing come down and you begin to feel well again.
That scenario is easy for all of us as parents to imagine. But how many times a day do you find yourself questioning someone else’s statements, facial expressions, etc.? Do you sometimes not believe someone—not because of their words but rather because of their facial movements, or their actions? In other words, what you see and what you hear don’t match up very well in your mind. Do you ever feel a little edgy when that happens, or a little on guard? This is your social vagus at work with your higher brain. It is working with your higher brain’s process of perception to determine if your social scenario warrants an alarm response or if you can relax and be at ease.
As you can suppose, this is a very important function of the nerve system. Consider the social connotations in our lives: social media, television and radio streams, texting and e-mail, etc. Do you feel your life more relaxed or in a constant state of go? The state of our “social” vagus is tremendously important to our health and well-being, since a constant state of alarm can lead to a tendency toward chronic illness.
From an anatomical perspective, the vagus nerve courses through the front part of our neck primarily in a sheath that also contains the internal jugular vein and carotid artery. It is well housed and protected for the most part. However, it’s vulnerable in the very uppermost area of our neck, the upper cervical area, where we have the ability to turn our heads from side to side. On occasion, due to chronic lifestyle habits, computer use, and poor posture, we may develop differences in muscle tone from one side to the other; these can make us prone for vertebral misalignments, or what chiropractors refer to as subluxations. Subluxations represent dysfunction in how joints and articulations should function. When a person has a tight or restricting muscle on one side of her neck it can cause a difference in how the spinal joints move and function, resulting in subluxation.
The converse is true as well. If a joint is subluxated, then the input from that joint to the nerve system is altered. Every joint sends information into the nerve system from a group of receptors. These receptors are located in the joints of the skull and spine and inform the nerve system where your head is in space at all times. Subluxations alter input from these receptors and give the nerve system a false sense of head position. This can result in further alterations of muscle tone, function, and ultimately how you perceive your environment. These subluxations can affect the development of higher centers of a child’s brain, affecting the “alarm” response and vagal tone. This puts a child at risk of developmental delay, emotional outbursts, digestive difficulties, and oversized behavioral reactions. There may also be delayed milestone acquisition in gait, crawling, and language and motor skills.
In the newborn, even the smallest of misalignments and subluxations may have a tremendous impact on the developing nerve system. Research and scientific studies continue to show that subluxations, alterations in the cranium of the newborn, and strain of the small muscles that hold the head upon the spine can impact neurological development in both the motor and cognitive domains. Chiropractic adjustment serves to remove subluxations and reduce any interference in function to the nerve system, thus allowing optimal expression of health and life. Considering the birth process, anatomical location of the vagal nerve in the upper neck, and the developmental impact of the subluxation, one can easily understand the importance of having all newborns, infants, toddlers, and children evaluated for the presence of subluxation and failure to meet milestones.
Vagal tone and function has become increasingly important to our health as we learn of its implications in not only heart, lung, and gut health, but now also in our social well-being. The ability to feel safe and loved, comforted and content— to reduce our alarm responses to appropriate levels, to better develop coping skills, and most of all to understand that we are ultimately better together, is the primary function of the social vagus. This is key to newborn development and our well-being throughout the rest of our lives.
SOURCE: “Chiropractic for Social Well-Being.” Michael W. Hall, D.C.; Pathways to Family Wellness magazine, Issue #51.