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PART 1: Understanding The Vagus Nerve Role in your Stress Response

The vagus nerve is the longest nerve in your body and the main group of nerves of your parasympathetic nervous system. This system controls specific body functions such as your digestion, heart rate and immune system. These functions are involuntary, meaning you can’t consciously control them. It connects your brain to many important organs throughout the body, including the gut (intestines, stomach), heart and lungs.

The word "vagus" means “wanderer” in Latin, which accurately represents how the nerves wander all over the body and reach various organs. They exit from your medulla oblongata in your lower brainstem. Then, the nerves pass through or connect with your:

  • Neck (between your carotid artery and jugular vein)

  • Chest (thorax)

  • Heart

  • Lungs

  • Abdomen and digestive tract

Your left and right vagal nerves join to form the vagal trunk. They connect at your esophageal hiatus, the opening where your esophagus passes into your abdominal cavity (belly). The vagal trunk includes anterior (front) and posterior (back) gastric nerves that go to your abdomen.

Your vagal nerve branches are:

  • Inferior ganglion branch that serves nerves and muscles to your throat (pharynx) and voice box (larynx).

  • Superior ganglion branch that serves nerves to your spine and ear.

  • Vagus nerve branch that serves nerves to your heart, lungs and esophagus (tube connecting your mouth and stomach).

What conditions and disorders affect the vagal nerves?

Your vagus nerve can be involved with these conditions:

  • Gastroparesis: Gastroparesis occurs when damage to a vagus nerve stops food from moving into your intestines from your stomach. This vagal nerve damage can result from diabetes, viral infections, abdominal surgery and scleroderma.

  • Vasovagal syncope: Syncope is another word for fainting. Vasovagal syncope occurs when a vagus nerve to your heart overreacts to certain situations like extreme heat, anxiety, hunger, pain or stress. Blood pressure drops very quickly (orthostatic hypotension), making you feel dizzy or faint.

What are the signs of vagus nerve problems?

Vagus nerve conditions cause different symptoms depending on the specific cause and affected part of your nerve.

You may experience:

  • Abdominal pain and bloating.

  • Acid reflux (gastroesophageal reflux disease, GERD).

  • Changes to heart rate, blood pressure or blood sugar.

  • Difficulty swallowing or loss of gag reflex.

  • Dizziness or fainting.

  • Hoarseness, wheezing or loss of voice.

  • Loss of appetite, feeling full quickly or unexplained weight loss.

  • Nausea and vomiting.

The vagus nerve is also a key part of your parasympathetic “rest and digest” nervous system.

It influences your breathing (heart - lungs), digestive function (gut) and heart rate, and immune system, all of which can have a huge impact on your health.

Your left and right vagal nerves contain 75% of your parasympathetic nervous system’s nerve fibers. These fibers send information between your brain, heart and digestive system.

The vagus nerves are the 10th of 12 cranial nerves. The vagus is known as cranial nerve X, the Roman numeral for 10.

But what you really need to pay special attention to is the "tone" of your vagus nerve. Vagal tone is an internal biological process that represents the activity of the vagus nerve.

Increasing your vagal tone activates the parasympathetic nervous system, and having higher vagal tone means that your body can relax faster after stress, hence improving the quality of your rest, digestion and detoxification.

The VN play important roles in involuntary sensory and motor (movement) functions, including:

  • Digestion.

  • Heart rate, blood pressure and respiration (breathing).

  • Immune system responses.

  • Mood.

  • Mucus and saliva production.

  • Skin and muscle sensations.

  • Speech.

  • Taste.

  • Urine output.

In 2010, researchers discovered a positive feedback loop between high vagal tone, positive emotions, and good physical health. In other words, the more you increase your vagal tone, the more your physical and mental health will improve, and vice versa.

The vagal response reduces stress. It reduces our heart rate and blood pressure. It changes the function of certain parts of the brain, stimulates digestion, all those things that happen when we are relaxed.

— Dr. Mladen Golubic, MD, Medical Director of the Cleveland Clinic.

What’s interesting is that studies have even shown that vagal tone is passed on from mother to child. Mothers who are depressed, anxious and angry during their pregnancy have lower vagal activity. And once they give birth to their child, the newborn also has low vagal activity and low dopamine and serotonin levels.

Your vagal tone can be measured by tracking certain biological processes such as your heart rate, your breathing rate, and your heart rate variability (HRV).

When your heart rate variability (HRV) is high, your vagal tone is also high. They are correlated with each other.

For some exercises on how to tone your vagus nerve read the next blog post here.

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