The vagus nerve, explained

The vagus nerve is the leader of our inner nerve centre, also known as the 10th cranial nerve or cranial nerve X.  It’s the longest of the 12 cranial nerves in the body, and has the most extensive distribution because it passes through the neck and chest into the abdomen.  The vagus nerve controls the entire parasympathetic nervous system, our “rest-and-digest” or “feed and breed” activities.


Vagus nerve facts

  • There are two vagus nerves, one on each side of the body.
  • The vagus nerve starts in the medulla of the brainstem, travels down the side of the neck, into the chest then down into the abdomen. On its journey, it navigates many visceral organs including the heart, lungs, oesophagus, pancreas and intestines.
  • Named the vagus because it “wanders” sending out tiny fibres from the brainstem to the visceral organs.


It’s role in the body?

  • The vagus nerve is a two-way communicator, it transmits signals throughout the body and then sends them back to the brain.
  • It regulates the immune response, hunger hormones and food intake, anxiety levels, and Inflammation levels
  • The gut uses the vagus nerve like a walkie-talkie reporting back to the brain how we are feeling, our gut feelings are genuine.
  • It triggers off the parasympathetic nervous system responsible for calming organs after the stress response or ‘fight-or-flight’ adrenaline response to danger. This branch of the nervous system is not under conscious control.
  • It assists in regulating heart rate function, speech, perspiration, blood pressure, the process of digestion, production of glucose, breathing and many other functions.

The vagus nerve and health 

A well functioning vagus nerve will improve brain-body communication, help in balancing homeostasis and regulating organs. Research has shown that the health of the vagus nerves may be the missing link to treating many chronic conditions, including some inflammatory illness such as arthritis.


Vagal Tone

Vagal tone refers to the activity of the vagus nerve, research shows that a high vagal tone improves the body’s ability to regulate blood glucose levels, reset the immune system and turn off inflammation, reducing the likelihood of illnesses such as diabetes, cardiovascular disease and stroke. In contrast, research has linked low vagal tone with chronic inflammation which can damage blood vessels and organs if it continues when no longer needed.


Signs and symptoms of low vagal  tone

  • Indigestion
  • Gastrointestinal bloating and IBS
  • A hiatus hernia
  • Loose stools
  • Stress, fatigue and anxiety
  • Shortness of breath and prolonged hiccups
  • Migraine headaches
  • Hypertension (high blood pressure)

Causes of low vagal tone

  • Excessive alcohol consumption
  • Overeating spicy food
  • Poor sitting posture or “tech neck” (see previous post here)
  • Overstimulation of the vagus nerve can cause shortness of breath and prolonged hiccups
  • Stress, fatigue, and anxiety can inflame the nerve (it’s a vicious cycle).

Measuring vagal tone

When we inhale the heart rate slightly speeds and slows down when we inhale, the vagus nerve is responsible for controlling the heart rate via electrical impulses to the sinoatrial node of the heart. Doctors can measure vagal tone and cardiac health, with the difference between the inhalation and the exhalation heart rates. The more significant the difference, the higher the vagal tone, which is better for health.


Benefits of high vagal tone

  • Ability to relax more quickly after a stressful event
  • Less anxiety
  • Better blood sugar regulation
  • Decreased risk of stroke and cardiovascular disease
  • In most cases lower blood pressure
  • Better digestion due to proper production of digestive enzymes
  • Fewer migraines
  • Less likely to be affected by mood disorders or depression.

Self-help to improve vagal tone

The vagus nerve modulates the connection between respiration and heart rate, which means mind-body practices such as guided breathing exercises can slow heart rate and lower blood pressure.

A 2016 study reported that slow abdominal breathing also called diaphragmatic breathing was the most effective self-practice in increasing vagal tone. Participants effectively managed their prehypertension and improved their ability to control the fight, flight freeze or faint response using this simple activity.  Regular deep breathing is the wellness secret integral to many mind-body practices; somatic movement, mindfulness meditation, yoga, tai chi, Qi Gong, some Pilates (sadly not all – yet) Its also used in chanting, repetitive prayer, used in guided imagery and by some singers too.


Breathing exercise for the vagus nerve

If you feel under pressure, are stressing about a deadline or about to blow a fuse, or just need to relax a little try this simple and easy breathing exercise.

Tip: Breath in through your nose, deep into your abdomen or belly. Breathe out slowly and gently through your mouth, letting out as much air as you can.

  • Inhale for a count of 5
  • Hold that breath for a count of 3
  • Exhale for a count of 6 or 7 
  • Pause (wait) for a count of 3
  • Repeat until you feel back in control.

Tip: Breath in through your nose, out through the mouth. Exhale quietly and gently through your mouth, letting out as much air as you can.



How breathing helps,  here’s the science bit

Any type of deep, slow diaphragmatic breathing stimulates the vagus nerve, which activates the parasympathetic nervous system. This signals the heart to slow down, which in turn calms the nervous system as a whole.  The vagus nerve connects all of this signalling and triggers the release of the neurotransmitter acetylcholine telling the lungs to breathe, literally giving us to the breath of life.

Note: The body’s internal alarm system which activates a stress response is triggered by fast and shallow breathing, making the body think it’s under attack, getting it ready to react with a fight, flight, freeze, or fainting response.


In the next post

‘ Vagus nerve and your health ’. Ways to help the vagus nerve maintain your health, reduce stress, restore resilience. Plus how osteopaths support the vagus nerve and vagal tone wellbeing.

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