In our last post we talked about the effect stress has on our gut and our overall health, and we touched on the Vagus Nerve. In this post, we get a little deeper into the science of the Vagus Nerve.
So what is the Vagus Nerve?
The Vagus Nerve is the longest cranial nerve. It contains motor and sensory fibres and, because it passes through the neck and thorax to the abdomen, has the widest distribution in the body. It contains somatic and visceral afferent fibres, as well as general and special visceral efferent fibres.
The Vagus Nerve runs from the base of the brain through the neck and then branches out in the chest stretching all the way down to the abdomen.
It wanders down the body, touching the heart and almost all major organs on its way.
It works to regulate breathing, heart rate, muscles, digestion, circulation, and even the vocal cords.
It’s a major regulator of the peripheral nervous system, known as the “rest and digest“.
It can slow our pulse and lower our blood pressure.
It is also a central player in the gut-brain axis.
Cascade of events
As we discussed in a previous post, an imbalance of bacteria in your gut can lead to low neurotransmitter (a chemical released from nerve cells) production. This includes our “happy hormones,” i.e. serotonin and dopamine. Low levels off these hormones can cause symptoms such as anxiety, depression, and/ or lack of motivation.
When the brain feels severely stressed, it unleashes a cascade of other hormones that can affect the whole digestive system.
For instance, corticotropin-releasing hormone (CRH) is one of the body’s main alarm bells.
CRH tells your adrenal gland to start making cortisol and adrenaline. These are the chemicals that can give you the strength and energy to run or fight your way out of trouble (i.e. fight or flight).
CRH also turns off appetite, which explains why some people can’t eat anything when they’re severely stressed. At the same time, the steroids triggered by CRH can make a person hungry, which is why some people fight stress with ice cream, chocolate, or alcohol (think stress and weight gain).