In the complex and fascinating world of human physiology, our autonomic nervous system plays a pivotal role. It's an intricate network that governs everything from our heart rate to the subtleties of emotional expression. Central to this system is the vagus nerve, our tenth cranial nerve that runs from our brain to our pelvis, as so beautifully illustrated in the portrait to the left of this paragraph.
In this blog post, we will learn about the vagus nerve and polyvagal theory--that is, the theory that our vagus nerve is the MVP of our nervous system. We will learn what the polyvagal nerve is, its significance, and how it interplays with the parasympathetic nervous system.
What is the Polyvagal Theory?
Developed by Dr. Stephen Porges in the 1990s, the Polyvagal Theory revolutionized our understanding of the vagus nerve and its role in controlling the heart, lungs, and digestive tract, as well as its influence on social behavior and emotional regulation. The theory posits that the vagus nerve, which is the tenth cranial nerve, has two distinct branches that affect our physiological state and psychological experiences in different ways.
The Two Branches of the Vagus Nerve
The Ventral Vagal Complex: This branch is myelinated, meaning it has a fatty covering that allows for faster communication. It's associated with social engagement behaviors, calming the heart rate, and facilitating facial expressions and vocalization. It's primarily responsible for the 'rest and digest' functions, promoting growth, healing, and restoration.
The Dorsal Vagal Complex: This unmyelinated branch is evolutionarily older and is associated with the 'freeze' response in the face of perceived life threats. When activated, it can cause immobilization, feelings of dissociation, or fainting.
The Parasympathetic Nervous System: An Overview
The parasympathetic nervous system is part of the autonomic nervous system, which controls involuntary body functions. Its primary role is to conserve energy and restore the body to a state of calm after periods of stress or danger. It achieves this through various actions like slowing the heart rate, increasing intestinal and gland activity, and relaxing sphincter muscles in the gastrointestinal tract.
How the Parasympathetic Nervous System Works
The parasympathetic nervous system operates through a 'rest and digest' mode, counterbalancing the 'fight or flight' response of the sympathetic nervous system. It's essential for maintaining a state of balance or homeostasis in the body. When activated, it signals to the body that it's time to relax and recover, lowering stress levels, reducing blood pressure, and enhancing digestion and nutrient absorption.
Interaction Between the Polyvagal Nerve and the Parasympathetic Nervous System
The polyvagal nerve, particularly its ventral vagal complex, is a critical component of the parasympathetic nervous system. It's what allows the body to shift from a state of arousal or stress (sympathetic activation) to a state of relaxation and social engagement (parasympathetic activation). This transition is not just physiological but also psychological, affecting our emotional and social behaviors.
The Role of the Polyvagal Nerve in Emotion and Social Connection
According to the Polyvagal Theory, the ventral vagal complex facilitates a calm state that is ideal for social interaction and bonding. This state is characterized by feelings of safety and trust, and it allows us to engage in complex social behaviors. It's also essential for emotional regulation, helping us to respond to stress in adaptive ways.
The Impact of Dysregulation
When there is dysregulation in the polyvagal system, it can lead to various psychological and physical health issues. For instance, overactivation of the dorsal vagal complex (the 'freeze' response) is often linked to trauma responses and disorders like PTSD, anxiety, and depression. On the other hand, an underactive vagal system can lead to difficulties in social engagement and emotional regulation.
Practical Applications: Enhancing Vagal Tone
Improving the function of the vagus nerve, or 'vagal tone,' has become a significant focus in therapies aimed at reducing stress and improving emotional well-being. High vagal tone is associated with better physical and mental health, while low vagal tone is linked to inflammation, depression, and negative moods.
Techniques to Improve Vagal Tone
Deep Breathing: Slow, deep breathing stimulates the vagus nerve and promotes relaxation. This can be box breathing, diaphragmatic breathing, or simply "belly breathing."
Cold Exposure: Anyone who has splashed cold water on their face has done this. A better version of splashing cold water is briefly lowering your face and head into a sink full of cold water. This triggers what is called the mammalian dive reflex, which is at its most simple explanation bradycardia, or a lowering of the heart rate. Brief cold showers activate the vagus nerve, as well. Your shower does not have to be full-on cold. Many health experts promote ending a shower with cool water. (**Be aware that those with decompensated heart failure should avoid sudden cold shocks, such as ice baths or sudden cold showers.)
Singing, Humming, and Chanting: These activities can stimulate the vagus nerve due to its connection to the vocal cords and the muscles in the back of the throat.
Meditation and Yoga: Both practices have been shown to increase vagal tone and improve overall well-being.
Positive Social Relationships: Engaging in supportive social interactions can improve vagal function and emotional health.
Jaw Muscle Relaxation: Part of the vagus nerve connects in our jaw, soft pallet, and tongue. Consciously unclenching, releasing, and relaxing the jaw can have a profound effect on vagal tone. This is quick, easy, and can be done often throughout the day whether in response to stress or simply to tone your vagus nerve and maintain a positive state of parasympathetic activation.
Relax The Muscles Around Your Eyes: I wrote a blog several months back on the innervation of our extraocular muscles and parasympathetic nervous system. Allowing your facial muscles to go slack, your eye muscles to relax, and your eyes to naturally widen (reducing the natural squint many people have), will tone your vagus nerve and activate a parasympathetic physiological response. Like jaw relaxation, this is also a quick and effective exercise to maintain parasympathetic activation and a state of calm.
Conclusion
The Polyvagal Theory and our understanding of the parasympathetic nervous system have opened new vistas in understanding human behavior, particularly in how we respond to stress and trauma, and how we can foster resilience and well-being. By learning to activate and tone our vagus nerve, we can significantly enhance our physical and emotional health, leading to a more balanced and fulfilling life.
Incorporating simple practices like deep breathing, meditation, and positive social interactions into our daily routines can strengthen our parasympathetic nervous system and help us navigate the challenges of modern life with greater ease and harmony. As we continue to explore the complexities of the human body, the Polyvagal Theory stands as a testament to the incredible interplay between our physical and emotional worlds, offering a path to deeper understanding and improved health.