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Vagus Nerve

Vagus Nerve

The Vagus nerve is also called the X cranial nerve or 10th cranial nerve, the longest and most complex cranial nerve. Its name is derived from the Latin ‘vagary’ – meaning “wandering.” It is sometimes referred to as the wandering nerve. This is because the Vagus nerve wanders from the brain into organs in the neck, chest, and abdomen. The Vagus nerve travels from the brain through the face and thorax to the abdomen. It is a mixed nerve that contains parasympathetic fibers.

The Vagus nerve acts as the body’s superhighway, sending information between the brain and internal organs and regulating the body’s response to relaxation time.

The Vagus nerve is actually a pair of nerves that emerge from the left and right side of the medulla oblongata portion of the brain stem and branches out in many directions to the neck and torso, where it’s efficient for actions such as carrying sensory information from the skin of the ear, influencing your immune system and regulating the muscles that you use to swallow and speak.

Vagus Nerve Branches

Vagus nerve branches

1. The Vagus nerve has two sensory ganglia (masses of nerve tissue that transmit sensory impulses):

  • The superior ganglia: The branches of the superior ganglion innervate the skin in the concha of the ear. 
  • The inferior ganglia: The inferior ganglion gives off two branches: The pharyngeal nerve and the superior laryngeal nerve

The recurrent laryngeal nerve branches from the Vagus in the lower neck and upper thorax to innervate the larynx muscles (voice box). 

2. The Vagus nerve also gives off cardiac, esophageal, and pulmonary branches. 

3. In the abdomen, the Vagus nerve innervates the more significant part of the digestive tract and other abdominal viscera.

4. The Vagus nerve has the most extensive distribution of the cranial nerves. 

The function of the Vagus nerve

A tremendous significance of the Vagus nerve is that it is the largest parasympathetic nerve in the body, supplying parasympathetic fibers to all main organs of the head, neck, chest, and abdomen.

  • Sensory: It is from the throat, heart, lungs, and abdomen innervate the skin of the external acoustic meatus and the internal surfaces of the laryngopharynx and larynx. It also provides visceral sensation to the heart and abdominal viscera.
  • Special sensory: It provides taste sensation to the epiglottis and top of the tongue.
  • Motor: It provides movement functions for the muscles in the neck (pharynx, soft palate, and larynx) responsible for swallowing and speech.  
  • Parasympathetic: It is responsible for respiration, digestive tract, and heart rate functioning. It innervates the smooth muscle of the trachea, bronchi, and gastrointestinal tract and regulates heart rhythm. 

 The function of Parasympathetic branches

  • The pharyngeal and laryngeal branches of the Vagus nerve transmit motor impulses to the pharynx and larynx.
  • The Cardiac branches of its act to slow the rate of heartbeat.
  • The bronchial branch of its acts to constrict the bronchi.
  • The esophageal branches of its control involuntary muscles in the esophagus, stomach, gallbladder, pancreas, and small intestine, stimulating gastrointestinal secretions and peristalsis.

Other Vagus nerve Function

  • Communication between the gut and the brain: The Vagus nerve delivers information from the gut to the brain.
  • Relax with deep breathing: The Vagus nerve communicates with the diaphragm. With deep breathing, a person feels more relaxed.
  • Reducing Inflammation: The Vagus nerve sends anti-inflammatory signals to other parts of the body.
  • Control vital aspects of the human body: The Vagus nerve helps control many vital aspects of the human body, including heart rate, blood pressure, sweating, digestion, and even speaking. Because of this, medical science has long been looking for ways of modulating the function of the Vagus nerve.

Effect of Vagus nerve on the body

  • Lowering heart rate and blood pressure: When the Vagus nerve is overactive, it can cause the heart to be inadequate to pump enough blood around the body. In some cases, unnecessary Vagus nerve action can lead to loss of consciousness and organ damage.
  • Fear management: The Vagus nerve sends information to the brain through the gut, linked to stress, anxiety, and fear. Hence the saying, “gut feeling.” These signs help a person to recover from stress and terrible situations.
  • It contains both motor and sensory information, and it provides innervation to the heart, large arteries, airways, lungs, esophagus, stomach, and intestines.
  • The Vagus nerve helps control the many muscles of the throat and voice box. It plays an essential role in regulating the heart rate and keeping the gastrointestinal tract in working order. It also carries sensory information from the internal organs back to the brain.
  • The Vagus nerve also helps with defecation, urination, and sexual arousal.
  • It is effective for the gag reflex (and the cough reflex when the ear canal is stimulated), controlling sweating, slowing the heart rate, regulating blood pressure, controlling vascular tone, and stimulating peristalsis of the gastrointestinal tract.​
  • In the stomach, the Vagus nerve increases the rate of gastric emptying and stimulates the production of acid.

Vagus nerve problems

Nerve Damage

Vagus nerve damage can have many symptoms because the nerve is so long and affects so many areas.

Possible signs of Vagus nerve damage include:

  • Difficulty speaking or loss of voice
  • A voice that is hoarse or wheezy
  • Trouble drinking liquids
  • Loss of the gag reflex
  • Pain in the ear
  • Unusual heart rate
  • Abnormal blood pressure
  • Decreased production of stomach acid
  • Nausea or vomiting
  • Abdominal bloating or pain

For someone, the symptoms depend on which part of the nerve is damaged.

Gastroparesis

Gastroparesis

Damage to the Vagus nerves can also lead to a condition called gastroparesis. This condition affects involuntary contractions of the digestive system, which prevents the stomach from being properly emptied.

Symptoms of gastroparesis include:

  • Acid reflux
  • Unexplained weight loss
  • Fluctuations in blood sugar
  • Abdominal pain or bloating
  • Feeling full shortly or loss of appetite immediately after starting a meal
  • Vomiting or nausea, particularly vomiting undigested food hours after eating.

Vasovagal syncope

Vasovagal syncope symptoms

Sometimes the Vagus nerves are affected further than certain stimuli, for example:

  • The blood sight or having blood drawn
  • Fear of bodily harm
  • Standing for a long time
  • Straining, including trying to have a bowel movement
  • Exposure to extreme heat

Remember, the Vagus nerve stimulates specific heart muscles that help lower the heart rate. When overused, it can cause a sudden drop-in heart rate and blood pressure, resulting in fainting. This is known as vasovagal syncope.

Vagus nerve stimulation

Vagus nerve stimulation is a medical procedure in which the nerve is stimulated with pulses of electricity used to treat various conditions. It is sometimes used for patients with epilepsy or depression that is otherwise untreatable; the technique has also been explored for Alzheimer’s-disease and migraine conditions.

Vagus nerve stimulation can be done either manually or through electrical pulses. Its effectiveness has been tested through clinical trials. Consequently, the United States Food and Drug Administration (FDA) has approved its use to treat two conditions.

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