What is the Vagus Nerve?

The vagus nerve is a primary carrier of information describing the state of the body to the brain, and transmitting information from the brain back to the body. It’s a feedback mechanism which is responsible for maintaining homeostasis for many of our vital organs and brain/body functions. Research over the past few decades shows that the vagus plays a key role in managing our levels of stress as well as our body’s inflammation; in this age of stress- and inflammation-related disease, it is perhaps the most important nerve in the body for us to be paying attention to.

What Does the Vagus Nerve Do?

BREATHING

The vagus nerve plays a key role in regulating the activity of the diaphragm. It sends signals from the brain to the diaphragm, facilitating its contraction and relaxation during breathing, and thereby modulating the respiratory rate and volume. This connection allows for precise control of respiratory movements, ensuring efficient gas exchange and oxygenation of the body. This fine-tuning mechanism ensures that the body receives an adequate supply of oxygen and maintains a balanced level of carbon dioxide.

SPEECH

The vagus nerve influences speech production through its connection to vocal cords, tongue, lips, and the respiratory system, and its role in regulating the muscles involved in articulation and phonation.

MOOD

As a key component of the parasympathetic nervous system, the vagus can rapidly offset your body’s stress response. As a cranial nerve (#10), it has a direct connection to the brain, specifically the limbic system, which is responsible for regulating emotions and mood.

FACIAL & VOICE EXPRESSIONS

Branches of the vagus control your facial muscles and the tone of your voice, both of which act as signals to the world, letting others know how you are feeling (and if it’s safe to interact with you).

DIGESTION

The vagus nerve is the main nerve in the enteric nervous system. The role of this system is to regulate digestive processes, including the secretion of hormones and enzymes that break down food into smaller particles that your intestines can absorb. The vagus nerve influences gut health by stimulating the release of digestive juices and hormones that enable you to digest food properly. It also helps move food through your digestive tract, so waste products are removed efficiently from your body.

HEART RATE & BLOOD PRESSURE

The vagus nerve plays a key role in regulating heart rate by releasing specific neurotransmitters that slow down the heart rate, promoting a state of relaxation.

IMMUNE FUNCTIONS & THE INFLAMMATORY REFLEX

Research has shown that the vagus plays an important role in regulating immune functions. Afferent vagal pathways transmit signals related to tissue damage and immune reactions to the brain stem. After central processing of these signals, activated efferent vagal pathways modulate inflammatory reactions through inhibiting the synthesis and secretion of pro-inflammatory cytokines by immune cells.

The Anatomy of
the Vagus Nerve

For those interested in a more detailed anatomical look at the vagus, this diagram shows the full scope of the vagus nerve, including its branches to various organs and body parts.

The vagus nerve is actually two bilateral nerves that extend from different parts of the brainstem and then join together just above the chest cavity. They have different roles: the right branch controls the heart and lower organs like the stomach, intestines, kidney, and liver, while the left branch is involved in speech, eye contact, facial expressions, and the ability to tune in to other people’s voices (in Polyvagal Theory terms, our ‘social engagement system’).

Image Credit:

Vagus Nerve Anatomy Polyvagal Institute PVI

Vagus Nerve Stimulation

We can stimulate the vagus nerve using natural means, such as breathing, playing, doing yoga, and more. View the image here for useful methods.

We can also stimulate the vagus nerve using "VNS devices" specifically engineered for that purpose.

Vagus Nerve Stimulation Devices

VNS devices fall into 2 general categories, those which are surgically implanted (iVNS) and those which are non-invasive (nVNS); both methods use electrical impulses that are carried by the vagus to the brain.

iVNS devices are typically used to treat headaches, epilepsy, stroke recovery and depression.

nVNS may be used for the same conditions as well as generally reducing stress, improving mood, lowering blood pressure and heart rate, and reducing inflammation.

Non-invasive VNS Options

Natural means of activating the vagus nerve are preferable in that they are usually free, or low cost, and can be integrated with one’s lifestyle on an ongoing basis. However, for those who wish to further enhance vagal activation and to explore the newest technological advancements in this field, PVI has curated a list of nVNS devices which are researched, safe, and available on the market. List coming soon, please check back.

Natural Methods of Vagus Nerve Stimulation Polyvagal Institute PVI

The Superhighway of Homeostasis

Humans have 12 pairs of cranial nerves (nerves which connect the brain to different locations in the body), the vagus being #10. Its name comes from the Latin, meaning ‘wandering’, as the nerve meanders from the base of the brain all the way down to the gut. It’s a two-way highway, carrying sensory information from the body to the brain (afferent nerves) and motor information from the brain to the body (efferent nerves).

The vagus comprises a majority (~80%) of the activity of our Parasympathetic Nervous System (PNS), which is sometimes described as our ‘rest and digest’ function in contrast to our Sympathetic Nervous System (SNS), which is often described as our ‘fight or flight’ function. It helps us recover and relax after expending a lot of energy, and it helps us digest our food.

When the body needs to mobilize, as in a state of stress, danger, or even play, the sympathetic nervous system kicks into action: muscle tone tenses, heart rate picks up, and your critical thinking is reduced as your body prepares for action. The vagus nerve acts as a counterbalance, and once the need for action is over it activates the parasympathetic nervous system to restore calm and balance. This intricate interplay between the sympathetic and parasympathetic systems is crucial for overall well-being and is sometimes referred to as ‘vagal tone.’
80% of the vagus nerve fibers are dedicated to the afferent function, i.e. sending sensory feedback from the body to the brain. 20% of its fibers are dedicated to efferent activity, sending motor information from the brain to the body.

Polyvagal Theory posits that the vagus nerve is divided into two branches (hence, ‘poly’): the ventral vagus and the dorsal vagus. The ventral vagus is responsible for promoting social engagement and connection, regulating emotions, and promoting feelings of safety and security. The dorsal vagus is associated with the ‘freeze’ response, which is activated in times of threat or danger. This branch of the vagus is responsible for shutting down non-essential bodily functions and conserving energy during times of stress. Polyvagal Theory posits that the autonomic nervous system is hierarchically organized, with the ventral vagus being the most evolved and sophisticated system for regulating social behavior and emotional responses. By understanding the role of the vagus nerve in mediating our response to stress and safety, we can gain insight into how our nervous system influences our behavior, emotions, and relationships.

In Polyvagal Theory, the social engagement system is linked to the vagus nerve, specifically, the ventral vagus. The ventral vagus network is activated when we are feeling safe, enabling us to engage in social interaction. When the ventral vagus is activated, it helps to calm the body’s stress response, lower heart rate, and enable higher brain functions which are helpful in promoting relaxation, creativity, social interaction, and sending cues of safety to let others know we are open to engaging with them. On the other hand, disruptions such as trauma or chronic stress can dysregulate the ventral vagus and lead to difficulties in social interactions, emotional regulation, and feelings of safety and trust.