Vagus

The vagus or pneumogastric nerve or cardio-pneumo-enteric nerve is Xe pair of the cranial nerves. It is a very important way of the vegetative regulation (digestion, heart rate…) but also of control sensorimotor of the Pharynx and thus of the Phonation.

The vagus is the cranial nerve whose territory is widest. It is a mixed nerve which convoie information driving, sensitive, sensory and especially vegetative parasympathetic.

Within the parasympathetic system, it constitutes the principal efferent innervation of the Cœur. In 1921, Otto Loewi has, the first, highlighted the synaptic Transmission by showing that the stimulation of the vagus involved a secretion of Acétylcholine which induced a deceleration of the Cardiac rhythm. The vagus is more generally an important way of the Viscéromotricité of the apparatuses cardiovascular, trachéo-broncho-pulmonary and digestive like with the regulation of secretions of the glands Surrénale S, of the Pancréas, the Thyroïde, the glands endocriniennes and the digestive system. It transmits also viscérosensitives information (in particular the aortic blood Pression).

On the driving level, it innerve the muscles lévateurs of the Velum and certain muscles constrictor of the Pharynx and Larynx. It ensures also the transmission of the somatic sensitivity of the pharynx, the larynx, and the épiglotte as well as part of gustatory information .

Anatomy of the vagus

The nervous fibers (nervous nets) constituting the rachidian nerves themselves occur in small small islands of gray substance disseminated in the white substance of brain. Then each pneumogastric nerve leaves the brain-pan by the posterior torn hole, goes down in the neck (precisely behind of the jugular vein and the internal artery carotid), skirts the esophagus passes in the mediastin then the diaphragm and arrives in the abdomen where it finishes in many nervous nets distributed to the liver, the stomach for the vague left and the whole of the internal organs of the abdomen. Inside the pneumogastric nerve another nerve walks on: the recurring nerve which innerve vocal cords. It is about a mixed nerve because having driving and sensitive functions. Nevertheless, the principal function of the pneumogastric nerve is vegetative (automatism, autonomy). During its way it gives several branches for the diaphragmatic known bodies. One will find a higher branch laryngé , pharyngé , cardiac superior , a branch of the corpuscle carotidien , all fascinating birth with the plexiform ganglion (or lower ganglion of X). Other branches leave the nerve such as the branch scouring which passes under the artery under clavière on the right and the cross-country race of the Aorta on the left and which will involve itself in the thyroid cabin to finish itself with the union laryngo pharyngienne (of this scouring by the nerve cardiac means). We have then a branch oesophagien , pulmonary (who with his counterpart will form the pulmonary plexus), broncho pulmonary , cardiac inferior (three branches cardic forming the cardiac plexus) and of the trachéaux branches . Then the two waves will open out on the level of the visères and the plexus soléaire after being last in the opening of the diaphragm in company of the esophagus.

Cores of the vagus

The Neuron S préganglionnaires of the vagus emanate from the medulla on the level of the ambiguous cores and make synapse in the intramuraux ganglia of the targeted bodies.

Driving cortico-nuclear beams

Reports/ratios of the vagus

Action: the stimulation of the pneumogastric nerve is at the origin of the manufacture and the acetylcholine secretion which is the first chemical substance recognized like playing the part of neurotransmitter (or neuro-transmitter). It is secreted by a variety of nervous cells (neuron). Its role is to allow the passage of the nerve impulse whose conduction is done thanks to a zone of contact (synapse, synaptic slit) located between two nervous cells (neurons). Its principal effects are a deceleration of the frequency of the beats of the heart, a reduction in the gauge of the bronchi, a reinforcement of the contraction of the smooth muscles (autonomous muscles) of the digestive tract and an increase in the secretion of saliva and gastric juices. In conclusion, the functions of the pneumogastric nerve are driving, i.e. it ensures the innervation of the velum while intervening in swallowing (the fact of swallowing) and more precisely in the third time of this mechanism. It also has a driving action on the pharynx. These sensitive functions are the following ones: it transmits the sensitivity of the larynx and the sensitivity of the pharynx, the épiglotte, the veil and the base of the language (more precisely the adjacent part of this one). The vegetative function of the pneumogastric nerve interests the heart and the vessels which it moderates. The pneumogastric one also has a hypotensive function (reduction in the blood-pressure). The vegetative action of pneumogastric also applies to the glands suprarenals, the pancreas, thyroid, the glands endocriniennes, the trachéo-broncho-pulmonary apparatus and the digestive system.

Examination of the vagus

Clinical elements

Electrophysiological exploration

Pathology of the vagus

A faulty operation of the pneumogastric nerve involves occurred of syncopes from which certain patients suffer, being characterized by a special sensitivity of the autonomous nervous system (functioning in an automatic way, without intervention of the nervous system of the will) thanks to the action of the vagus. The symptoms are the following:

  1. a bradycardia
  2. a tendency to the syncopes and anxiety
  3. a myosis (reduction in the gauge of the pupils)
  4. a perspiration locating at the ends of the members
  5. an excessive secretion of saliva
  6. hyperchlorhydria (excess of secretion of hydrochloric acid by the stomach)
  7. a constipation
  8. Of the spasms
  9. Of the episodes of diarrhea and disorders of breathing
  10. a faintness vagal
The syncope corresponds to the loss of consciousness, brutal and supplements, secondary with an anoxia (absence of oxygenation due itself to an insufficiency of blood contribution) of the brain, occurring brutally. The patients having this type of affection present an extreme paleness and generally a reversible respiratory stop and of short duration. A lesion of the vagus can also be at the origin of dysphagie (difficulty of swallowing) or of a dysphonie (difficulty of emitting sounds). This pathology occurs primarily when there exists a lesion of the branches pharyngiennes of this nerve. Certain patients also present an anesthesia of the upper part of the larynx and a paralysis of the crico-thyroid muscle at the origin of a weakened voice or an increased fatigability of this one. Various pathologies are likely to resound on the normal functioning of the pneumogastric nerve. It can be a question, inter alia, of an aneurism of the arc of the aorta, of a compression of origin tumoral on the level of the médiastin (zone containing the heart and located between the lungs), of a lung cancer. An surgical operation of the neck also can lésionner the pneumogastric one. The paralysis of the two recurring laryngés nerves involves a aphonie, i.e. a loss of the voice, and a respiratory stridor i.e. a strident respiratory noise whose tonality is very high. A pathology of thyroid gland is also likely to resound on the pneumogastric one. It is primarily the left recurring nerve which is most frequently injured, being given its longer way.

Internal bond

  • Neuroanatomie

External bond

  • http://www.vulgaris-medical.com/

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