Question

Smiling ,for example,can stimulate vagus nerve as written in the following quote:

Whether it’s through mindfulness, paced breathing, sports, sex or simply smiling, increased vagal tone is important for good health and wellbeing. There is a lot of hype online and some of it may be over the top. But reduced stress and greater relaxation are safe for everyone and have positive effects for our body and brain.

In above quote vagus nerve is stimulated by increased vagal tone.

My question is - What is meant by increased vagal tone ? Can pain also stimulate vagus nerve and increase vagal tone ?

Answer 1

Increased vagal tone means a higher level of activity of the vagus nerve, resulting in a lowered heart rate and a state of relaxation. Positive experiences and practices like smiling and deep breathing can sustainably increase vagal tone, while pain can cause a transient stimulatory effect on the vagus nerve, often leading to a decrease in heart rate or fainting in the case of vasovagal syncope.

Step-by-step explanation:

Increased vagal tone refers to a heightened level of activity of the vagus nerve, which is part of the parasympathetic nervous system. This heightened activity results in the release of acetylcholine (ACh), which slows heart rate (HR) by opening potassium ion channels. This action extends the repolarization of the heart's pacemaker cells, spacing out the intervals between heartbeats and thereby lowering the heart rate. In other words, increased vagal tone helps maintain a slower, steadier heart rate that is often associated with a state of relaxation and well-being.

Stimulation of the vagus nerve can indeed arise from various sources. While positive stimuli like smiling, deep breathing, and relaxation techniques are known to increase vagal tone, pain can also stimulate the vagus nerve; however, it usually does so in a way that can lead to reflex responses such as a decrease in heart rate or even fainting, known as vasovagal syncope. This reflex involves a sudden increase followed by a decrease in vagal tone, which might temporarily increase parasympathetic output, but in this case, it’s a transient response to stress rather than a sustained increase in resting vagal tone.

It is important to distinguish between the beneficial aspects of increased vagal tone brought about by relaxation and healthful activities from the acute response to pain or distress that activates the vagus nerve in a different context.