What is the Vagus Nerve?
It is a pair of nerves that begins at the brain stem and follows the spinal cord innervating most organs. It touches every system of the body and includes both sensory and motor functions. It engages the parasympathetic nervous system and regulates digestion, heart rate, mood, and speech among other functions.
The Vagus Nerve and the Autonomic Nervous System
The vagus nerve plays a role to aid the autonomic nervous system (ANS) in mobilizing for a threat (SNS) and down-regulating the systems after the threat ends (PNS). It’s like the radio waves taking signals from the brain to tell the body and the organs what to do and when.
Polyvagal Nerve Theory
Modern science suggests that we are always somewhere on a spectrum that Dr. Stephen Porges coined as the Social Engagement System. Dr. Porges has been studying the vagus nerve and has given us new science that says we are always somewhere between socially engaged (calm/at ease), mobilized/hypervigilant (fight/flight), or immobilized (freeze/fold). Both the SNS and the PNS are responding to our environment with the help of the vagus nerve.
His theory also suggests that stimulating the vagus nerve and improving what is called vagal tone can be a tool that we can use to override the ANS and help bring us back to balance more quickly and easily. You can learn more about polyvagal nerve theory and its impact on your health at Dr. Porges’ organization is called https://www.polyvagalinstitute.org.
How Does the Vagus Nerve Respond to Threats?
Here’s a modern example of how the ANS and the vagus nerve work to respond to a threat. Imagine you and a friend are sitting in your home having tea and a chat. There are no immediate threats, and both you and your friend are laughing while sharing stories. This is what is called “socially engaged.”
Then, someone suddenly knocks very aggressively at your front door. Although you were just laughing about a story, now you are both instantly moved from socially engaged to hypervigilant. Your body is ready to fight or flee.
You go to your door and discover your roommate, who was locked out and wanted to be sure you could hear her knocking. Suddenly, you let out a sigh of relief, moving back towards social engagement and calm. This is the ANS and the vagus nerve at work. They are responding to the signals coming from your brain based on your environment.
Now let’s dig into the brain a bit more, specifically the limbic system, and learn how it is working to respond to threats.
As soon as you heard the loud bang at the door, your amygdala sent a signal to the hypothalamus to say, “ALERT- incoming threat.” Then the hypothalamus, which acts as the command center for the central nervous system, registers the threat and tells the ANS to get ready. Stress hormones flood your system, initializing the “stress response.”
In addition to alerting the hypothalamus of the threat, the amygdala also reports and records all of the sensory and emotional information to the hippocampus, which in turn creates a memory of what has happened. This memory is designed to help us avoid a threat in the future.
This memory is how we learn to not touch a hot flame after experiencing the pain the first time and is also why we can be triggered into a stress response from seemingly out of nowhere. In our scenario, your hippocampus will encode a memory of the tea, the lighting in the room, and any smells or sensations that were happening at the time of the event or perceived threat.
Vagus Nerve Stimulation and Vagal Tone
Vagus nerve stimulation is a method of improving vagal tone, which is the indicator for how well your vagus nerve is functioning. By improving your vagal tone, you can improve your body’s natural ability to engage the parasympathetic nervous system and recover homeostasis after a trauma.
Here are some quick and easy ways to stimulate your vagus nerve and improve vagal tone.
- Singing or humming
- Cold shower or exposure to cold
- Yoga asana
- Alternate nostril breathing