THE VAGUS NERVE

THE PARASYMPATHETIC NERVOUS SYSTEM & REST AND DIGEST MODE

Think of any meditative or mindfulness practice you have engaged in. Breath control and awareness are at the heart of many of them - especially the voluntary slowing or deepening of the breath. Many, (but not all!) of the benefits that come from these practices are due to the voluntary slowing down of our breathing. These impacts are both physical and mental.

Slow breathing techniques enhance interactions between our autonomic nervous system (the part of our nervous system that runs on its own) and psychological control (the part that lets us control actions/movements etc). 

Slow breathing techniques seem to promote a predominance of the parasympathetic nervous system - what we call our “rest and digest” system. This is in opposition to our sympathetic nervous system - what is often activated in stress responses and called our “fight or flight” response. 

This parasympathetic activation and deep breathing is mediated by the activity of a nerve called the vagus nerve. The vagus nerve has been gaining popularity in health and wellness spheres - and for good reason. This nerves function explains some of the ways how breathing and meditation can impact stress, relaxation and digestion - pretty cool!

The vagus nerve connects to several organ systems and is both sensory - takes information TO the brain - and motor - activates our muscles. For context - most nerves often have ONE of these functions, not both.

The vagus nerve transmits information from the gastrointestinal tract, the cardiovascular and pulmonary systems and diaphragm (and more!) to the central nervous system (our brain!). It also sends information to some organs as well!

When we enhance “vagal tone” - how much the rest and digest system is activated versus the fight or flight - we see heart rate variability increase. 

Heart rate variability is a measure of change in the time in-between each heart beat. The more we are in fight or flight mode - the lower our heart rate variability is. The more relaxed we are - the longer it is. This measure is often used to see how recovered athletes are or how stressed or burnt out people are.

Heart rate variability increases with slow breathing. Partially because of the physical changes with inhalation (and pressure in your thorax) and exhalation, but also because of an increase in activation of the vagus nerve. 

Breathing impacts our stress response from this physiological change but also from our ATTENTION. When we focus on our breath we have a voluntary shift in attention. We are creating our own calm, a shift into rest and digest mode, through our attention and in turn through the breathing itself.