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The vagus nerve is the name of the tenth cranial nerve, most likely due to how this structure works - the vagus nerve extends from the skull to the deep regions of the abdominal cavity, giving off branches to many structures in the body. What is the role of the vagus nerve?

The vagus nerveis the tenth among twelve pairs of cranial nerves. Of all the cranial nerves, it is thenerve Xthat is the longest and has the greatest number of functions. The vagus nerve conducts both afferent (afferent, sensory) stimuli to the central nervous system and centrifugal (efferent, motor) stimuli. In addition, parasympathetic fibers belonging to the autonomic nervous system also run within this nerve.

The vagus nerve delivers sensory stimuli to the brain, carries effector fibers to muscles, and has fibers that belong to the autonomic system. It is quite an interesting nerve - e.g. excessive activity may lead to fainting. There are also treatments that are carried out within this nerve - the effects can be obtained both by cutting it and by stimulating the vagus nerve.

Vagus nerve: structure

The fibers of each cranial nerve begin in the brain stem. In the case of the vagus nerve, its nuclei and ganglia are located within the medulla and are:

  • ambiguous nucleus from which the motion fibers come
  • dorsal nucleus where parasympathetic fibers originate
  • upper and lower ganglion from which the sensory fibers begin

From the inside of the skull, the vagus nerve exits through the opening of the internal jugular vein. Then it runs down the body in the so-called the neurovascular bundle (along with the common carotid artery and the internal jugular vein). The vagus nerve eventually reaches the mediastinum and continues adjacent to the esophagus. It then travels downward, passing - through the hiatus of the diaphragm - into the abdominal cavity. There, the vagus nerve forms two trunks, referred to as anterior vagus trunk and posterior vagus trunk. Throughout its course, the vagus nerve gives off the following branches:

  • tire
  • ear
  • pharyngeal (forming together with the branches of the glossopharyngeal nerve the so-called pharyngeal plexus)
  • superior laryngeal nerve
  • for carotid sinus
  • cardiac (cervical and thoracic)
  • nerveretrograde laryngeal nerve (eventually passing into the inferior laryngeal nerve)
  • tracheas
  • bronchial
  • esophagus
  • mediastinal
  • pericardial
  • hepatic
  • gastric
  • visceral (for visceral plexus)

Vagus nerve: functions

Looking at how many branches the vagus gives off, a wide range of functions is clearly visible. The vagus nerve is responsible for:

  • innervation of the back of the skull
  • reception of sensory stimuli in the area of ​​the auricle, the external auditory canal and the eardrum
  • innervation of the soft palate and pharynx
  • managing the motor activity of many muscles (such as the cricothyroid muscle, levator soft palate, palatopharyngeal and palatopharyngeal muscle, laryngeal muscles), thanks to which this nerve is involved both in controlling food swallowing and in the process of the formation of speech
  • conduction of stimuli in the area of ​​the parasympathetic autonomic system (the vagus nerve controls the heart, gastrointestinal function, also influences sweating and controls the parasympathetic system in the respiratory system)

The vagus nerve is also involved in reflex actions. The reflexes that arise as a result of his participation include the gag and cough reflexes.

Vagus nerve: causes and symptoms of damage

Damage to the vagus nerve can be caused by damage to the centers from which the fibers of this nerve originate, as well as damage to the fibers of the vagus already outside the cranial cavity. This can happen as a result of damage to the brain stem (e.g. due to trauma or ischemia), as well as as a result of deep wounds made in the neck area. Symptoms of vagal injuries in such situations can be:

  • drooping soft palate
  • deviation of the tab in the direction opposite to the damage
  • speech articulation disorders related to laryngeal muscle paralysis

There are also syndromes in which one of the problems is vagal palsy. Examples of such units are:

  • bulbar palsy (where, in addition to palsy of the X nerve, there are also palsy of the IX and XII nerves),
  • pseudo-bulb paralysis (in which, apart from the disorders of the X nerve, there are also pathologies concerning the V, VII, IX and XII cranial nerves),
  • Wallenberg's syndrome (with accompanying palsy of the V and IX nerves and with Horner's syndrome).

Vagus nerve: vasovagal syncope

Likealready mentioned when discussing its functions, the vagus nerve affects how the heart works. In general, the action of this structure on the heart is based on slowing down its activity - as a component of the parasympathetic system, the vagus nerve acts antagonistically to the sympathetic nervous system, which accelerates the heart rate. Under normal circumstances, there is a balance between these two parts of the autonomic system, but in some situations one of them is advantageous - such is the case of vasovagal syncope caused by overactivity of the vagus nerve. emotions or seeing blood. A fairly common cause of vasovagal syncope is rapid adoption of an upright body posture (especially if this act was preceded by lying down). Occasionally, the vagus nerve becomes so excited that it causes the heart to slow down dramatically - it can even result in temporary asystole (cardiac arrest). Fainting in this case occurs because blood pressure is lowered and therefore blood flow to the central nervous system is reduced. Patients usually recover quickly from vasovagal syncope, most often within a minute of syncope. However, each case of fainting should be consulted with a doctor, as it is necessary to exclude all other possible causes of fainting.

Vagus nerve: nerve stimulation for healing purposes

Stimulation with electrical impulses of the vagus nerve has been used in medicine for a relatively long time - the first procedures of this type were started in 1997. The exact mechanism of the stimulation's action is not entirely clear. post-stimulation changes in neurotransmitter secretion. Currently, stimulation of the vagus nerve is used to treat severe forms of epilepsy and drug-resistant depression. However, there are ongoing studies on other possibilities of using vagal nerve stimulation, examples of which are the attempts to use this technique in the treatment of Alzheimer's disease, tinnitus or in the treatment of various types of anxiety disorders. Stimulation of the vagus nerve can also potentially be used in the treatment of chronic inflammatory diseases. such as rheumatoid arthritis and inflammatory bowel disease. It turns out that the tenth cranial nerve can reduce the production of pro-inflammatory factors in the body, such as TNF (tumor necrosis factor).cancer). Vagus nerve stimulation could therefore be an alternative for patients - currently, antibodies neutralizing them are used to reduce the amount of pro-inflammatory substances, in the future it may be possible to replace such therapy with implanting patients with vagal nerve stimulators. Everything remains a matter of research that is still being conducted, and the results of this research are also important - and these are extremely promising. According to reports from 2016, the use of vagal nerve stimulation may reduce the levels of laboratory markers of the disease in patients with rheumatoid arthritis.

Vagus nerve: vagotomy

Not only the stimulation of the vagus nerve can be used in the treatment of various diseases - cutting the fibers of this nerve, i.e. vagotomy, is also used. In the past, vagotomy found wider use, now it is only used when other methods have failed. This situation is related to the fact that peptic ulcer disease - which was the main indication for vagotomy - can now be successfully treated pharmacologically. Nowadays, vagotomy is performed mainly when the use of antibiotics and proton pump inhibitors does not achieve a satisfactory peptic ulcer treatment effect. Due to the fact that the vagus nerve carries information from centers related to the feeling of hunger and satiety, attempts have also been made to cut its fibers in obese patients. Currently - due to the inconclusive results of research on this procedure - vagotomy is not routinely used as a surgical method of obesity treatment.

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Category:

Neurology