THE VAGUS NERVE, THE VAGAL BRAKE, & VAGAL TONE

The vagus nerve is the longest and most complex of the cranial nerves. It extends from the brainstem all the way down to the abdomen. The vagus nerve is responsible for a variety of functions, including heart rate, digestion, and immune response.

Vagal tone is a measure of the activity of the vagus nerve. A high vagal tone indicates a high level of activity of the vagus nerve, which indicates increased sense of safety, compassion, and social openness around others. On the other hand, a low vagal tone indicates a low level of activity of the vagus nerve, which is associated with increased anxiety, fear, and isolation.

The vagus nerve is also responsible for the "vagal brake". The vagal brake is a mechanism by which the body can quickly alter heart rate and blood pressure in response to stress, and manages the shifts between the Ventral Vagal rest and Sympathetic stress responses. Therefore, exercises that strengthen the vagal brake can build resistance to stress and improve overall health.

There are a number of ways to measure vagal tone, but the most common is through heart rate variability (HRV). HRV is a measure of the variation in time between heartbeats. Generally, higher HRV indicates a high vagal tone, while lower HRV indicates a lower vagal tone.

The vagus nerve is an important part of the human body, and its activity can have a profound impact on our health and well-being. By understanding the vagus nerve, the vagal brake, and vagal tone, we can take steps to improve our health and resilience in the face of stress.