The Vagus Nerve Unveiled: Understanding the Buzz

The vagus nerve carries approximately 75% of the parasympathetic nervous system (PNS) nerve fibres and is stimulated by slow, deep breathing (particularly through the nose). This stimulation sends signals to various organs in the body, including the heart, promoting a state of relaxation. Extending the length of expiration directly stimulates the vagal nerve (which is also called an increase in vagal tone and some refer to this as resetting vagal tone).  Resetting or increasing  vagal tone can also be achieved through exercise, electrical stimulation of the nerve, massage (particularly to the ear) and mindfulness meditation.

Increasing vagal tone leads to:

1. Reduction in release of stress hormones: Deep breathing has been shown to decrease the levels of stress hormones such as cortisol and adrenaline in the bloodstream. This reduction helps alleviate the physiological arousal associated with stress.
2. Heart Rate Variability (HRV): Deep breathing increases heart rate variability, which is the variation in time between successive heartbeats. The heart rate increases during inhalation and decreases during expiration. Higher HRV is associated with better resilience to stress, and a more adaptive autonomic nervous system. Better health and disease outcomes are associated with higher HRV. There is also a correlation between HRV and cognitive ability.
3. Activation of the Baroreflex: The baroreflex is a natural mechanism that helps regulate blood pressure and is regulated by the SNS and PNS. Deep breathing increases the sensitivity of the baroreflex contributing to the stabilisation of blood pressure and overall cardiovascular health.
4. Enhanced Oxygenation: Deep breathing ensures a more efficient exchange of oxygen and carbon dioxide in the lungs. Proper oxygenation is essential for cellular function and energy production, promoting a sense of well-being.
5. Mind-Body Connection: Focusing on the breath promotes mindfulness, diverting attention away from stressors and calming the mind. The mind-body connection plays a significant role in triggering the relaxation response.

In summary, deliberate and mindful breathing patterns activate the parasympathetic nervous system, leading to a cascade of physiological responses that counteract the stress response. Incorporating deep breathing exercises into daily life to reset vagal tone can be a powerful tool for promoting relaxation, reducing stress, and enhancing overall well-being.