Vagus nerve: summary anatomy, functions and pathologies

The vagus nerve (also called pneumogastric nerve or, in English vagus nerve ) is the tenth nerve belonging to the group of 12 cranial nerves (X cranial nerve). The vagus nerve starts frommedulla oblongata and leads, through the jugular hole, downwards in the thorax and abdomen. The 2 left and right vagus nerves are among the most important in the body as well as the longest and most branched of the cranial nerves.

Etymology

The name “vagus” comes from the Latin “vagus”, which means “vagabond” to describe the fact that this nerve – after leaving the medulla oblong – “vagabonds” within our body, reaching areas even very distant from its origin .

Functions

The vagus nerve is primarily responsible for:

  • heart rate;
  • gastrointestinal peristalsis;
  • sweating;
  • sensations from the viscera of the neck, thorax and abdomen;
  • some mouth movements (including those that allow you to speak);
  • airway patency (keeping the larynx open).

It also receives sensations from the external ear (through Alderman’s nerve) and part of the meninges. One of its main purposes is to stimulate the production of gastric acid and regulate the movements made by the stomach and intestines during the digestion phase, it also provides innervation by the parasympathetic autonomic nervous system of the heart; the right vagus innervates the sinoatrial node and its stimulation induces bradycardia (slowing of the heart rate).

The functions of the vagus nerve can be summarized and divided into:

  • parasympathetic functions: the vagus nerve is responsible for:
    • decrease in heart rate (bradycardia);
    • increase in secretions from the digestive tract (salivary, gastric, pancreatic, biliary and intestinal);
    • increase in intestinal peristalsis, promoting digestion;
    • contraction of the bronchial muscles;
    • dilation of the innervated arterial vessels (vasodilation);
  • general somatic sensory function: the vagus nerve collects general somatic sensitive information from the meninges, from a skin area of ​​the auricle and from the mucous membrane of the pharynx and larynx;
  • general visceral sensory function: the vagus nerve carries general visceral sensory information from the larynx, the lower portion of the trachea, the esophagus, the thoracic and abdominal organs and the sinus and carotid glomus;
  • special visceral sensory function: the vagus nerve carries gustatory information from the root of the tongue;
  • motor function: the vagus nerve controls the following muscles:
    • palatoglossus;
    • palatofaringeo;
    • Palatine veil elevator;
    • salpingofaringeo;
    • upper, middle and lower pharyngeal constrictors;
    • larynx muscles;
    • muscles of the proximal esophagus.

Anatomy and course

The vagus nerve comes out of the bulb through the groove of the mixed nerves with about ten radicles and runs forward laterally to the glossopharyngeal nerveand anterior to the accessory nerve, then it comes out of the skull through the jugular hole, forms the jugular ganglion and the gnarled ganglion, then runs vertically in the neck. Became independent of the glossopharyngeal and accessory nerves, it becomes part of the vascular and nerve bundle of the neck, consisting of antero-medially carotid artery and the antero-lateral internal jugular vein. The vagus nerve enters the thorax leaving the bundle and running, on the right, medially to the anonymous artery and medially to the superior vena cava, to the left, laterally to the aortic arch. It is posterior to the pulmonary ili and runs to the right, posterior to the esophagus, forming the right pulmonary plexus and the posterior esophageal plexus , to the left, anteriorly to the esophagusforming the left pulmonary plexus and the anterior esophageal plexus and giving life to the recurrent laryngeal nerve . The front and rear trunks are made up of mixed fibers, even if the rear component is mainly right and the front component is mainly left. The vagus nerve then enters the abdomen following the course of the esophagus, passing through the diaphragmatic esophageal orifice. In the abdomen the two trunks run on the anterior and posterior faces of the stomach forming the anterior and posterior gastric plexuses . The posterior branch then gives rise to the celiac branch and the celiac plexus , forming the memorable loop with the large right splanchnic nerve; the front branch gives rise toleft celiac plexus receiving the large left splanchnic.

Innervated organs

The parasympathetic component controls all the smooth muscle not controlled by the oculomotor, facial and glossopharyngeal nerves and by the spinal nerves, which control only some viscera (for example the last part of the intestine), in particular it innervates both the intestine and the stomach. The vagus nerve supplies parasympathetic fibers to all organs, except for the adrenal glands, from the neck to the second segment of the spine. The vagus also controls some skeletal muscles, including:

  • palatoglossus;
  • palatofaringeo;
  • Palatine veil elevator;
  • salpingofaringeo;
  • upper, middle and lower pharyngeal constrictors;
  • larynx muscles;
  • muscles of the proximal esophagus.

diseases

The loss or alteration of the function of the vagus nerve, for example in case of cervical arthrosis, will result in a loss of parasympathetic innervation for a very large number of structures with great consequences for the vital functions of the individual. The main effects of vagus nerve damage can include an  increase in blood pressure and heart rate . On the contrary, vagal hyperstimulation can induce severe bradycardia, the onset / worsening of an atrioventricular block and even the death of the patient, which for example happens in cases of asphyxiation during erotic practices or even with too tight shirt collars or ties . Symptoms and signs of vagus impairment may include:

  • nausea;
  • He retched;
  • constipation;
  • diarrhea;
  • anxiety;
  • tremors;
  • dysphagia (difficulty swallowing);
  • difficulty moving your mouth;
  • stomach acid;
  • dizziness;
  • dizziness;
  • redness in the face;
  • tachycardia or bradycardia (depending on the type of vagal alteration);
  • hypotension or high blood pressure;
  • neck pain and stiffness;
  • headache
  • pallor;
  • cold sweating;
  • reduced salivation;
  • difficult digestion;
  • cerebral hypoperfusion;
  • fainting;

Isolated vagus nerve dysfunction is rare but, if the conflict or injury is above the point where the vagus branches out for the first time, it can be diagnosed by a hoarse voice, due to the dysfunction of one of its branches , the recurrent laryngeal nerve.  Damage to this nerve can cause difficulty in swallowing.

Valsalva maneuver and carotid massage

Some medical procedures such as the Valsalva maneuver or carotid massage can have stimulatory effects on the vagus nerve and induce bradycardia. The Valsalva maneuver consists of a forced exhalation with the glottis closed; carotid massage consists of the pressure of two or three fingers in the area of ​​the neck corresponding to the carotid sinus. To learn more, read also:  Valsalva maneuver in medicine (tachycardia and vagus nerve)

Vagus nerve stimulation is sometimes used as a tool to reduce anxiety and psycho-physical stress

 

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