Getting to Know Your Vagus Nerve

The diagram above shows the tenth cranial nerve, also known as the vagus nerve. It comes from the amazing book ‘Gray’s Anatomy’, created in 1858 by Henry Gray with illustrations by Henry Vandyke Carter, both British anatomists and surgeons. The book has undergone multiple revisions, but still remains ‘the doctors’ bible’. This is my beautiful copy, a gift from my partner, a leather bound edition by Barnes and Noble:

The vagus nerve is the only cranial nerve that leaves the head and neck area, and is the longest nerve in the body. This nerve is central to the practice of yoga, as it is considered the gateway to the parasympathetic nervous system. To understand its relevance a little more, we need to take a brief look at the human nervous system.

The nervous system contains billions of cells called neurons, or nerve cells, which send and receive electrical signals through your body to tell it what to do.

The two main components of the nervous system are:

1. Central nervous system (CNS) - comprises the brain and spinal cord. Broadly, the three functions of the CNS are to take in sensory information, process information, and send out motor signals.

2. Peripheral nervous system - consists of many nerves that branch out from the CNS all over your body. This system relays information from your brain and spinal cord to your organs, arms, legs, fingers and toes. Your peripheral nervous system contains your:

  • Somatic nervous system - guides your voluntary movements.

  • Autonomic nervous system (ANS) - controls involuntary activities, such as heart rate, blood pressure, respiration, digestion, and sexual arousal. The ANS has two main anatomically distinct divisions:

    • Sympathetic nervous system - controls ‘fight or flight’ type responses;

    • Parasympathetic nervous system - controls ‘rest and digest’ type responses.

As yoga practitioners, even if we don’t know it, we are engaging deeply with our parasympathetic nervous system, and particularly with its essential component, the vagus nerve.

If we study the diagram, we can see that this nerve connects the brainstem with the cardiac area, the pulmonary area, and the stomach. These connections point us towards the main functions of the vagus nerve: it is mainly responsible for our relaxation response, telling our breathing and heart to slow, improving our digestion, and encouraging social connection.

Now, although the vagus nerve is part of the parasympathetic nervous system (PNS) (in turn part of the autonomic nervous system that controls involuntary movements), we can also interact with it; in effect it has a user interface! And, without knowing how this mechanism works, yogis have known and used this for centuries: by breathing deeply, down into our abdomen, and extending our exhalation, we stimulate the vagus nerve. In turn, this activates vagal pathways that counteract the flight or fight stress response, slowing the heart rate and fostering a feeling of calm relaxation.

A hospital nurse once said to me, when I was frozen with pain and fear, ‘Occupy yourself only with breathing’.

How right she was.

(See My Back Story for more about why I was in hospital.)

Thank you for reading! If you have enjoyed reading, you might also enjoy The Power of Yoga for Healing of Trauma.

My next Yoga Teacher Training programme starts in Feb 2024.

Bibliography

Gray, Henry (2008) Gray's Anatomy: The Anatomical Basis of Clinical Practice (40th ed.), Churchill-Livingstone, Elsevier.

Swanson, Ann (2019) Science of Yoga: Understand the Anatomy and Physiology to Perfect Your Practice, Dorling Kindersley.

Donna GerrardComment