Vagus nerve

The vagus nerve ( vagus short ) is the tenth ( X ) cranial nerve. It is the largest nerve of the parasympathetic nervous system and involved in the regulation of the activity of almost all internal organs. Its large area of ​​distribution was also namesake, the name derives from the Latin vagari ( " wander " ), so literally translated it means " the wandering nerve".

In addition to its vegetative function, he is involved in the motor control of the larynx, pharynx and the upper esophagus and transmits taste sensations from the tongue base and touch sensations from the pharynx, the larynx and part of the external auditory canal. Even the internal organs in the chest and abdomen are sensitive fibers reached ( Viszeroafferenzen ), but primarily serve the mediation of reflexes. This means that the vagus contains the following fiber qualities: Somatomotorisch ( voluntary control ), somatosensory (consciously perceived ), sensory (taste ), and viszerosensibel viszeromotorisch ( parasympathetic ).

The nerve is the IX. and XI. Cranial nerves ( glossopharyngeal nerve or accessory nerve ) also summarized the " Vagusgruppe ".

• 5.1 Medicine
• 5.2 Veterinary Medicine

Origin of the vagus

The cell bodies (soma, nerve cell bodies ) of the parasympathetic neurons within the dorsal motor nucleus of the vagus nerve are located in the vagus nerve (Veterinary Anatomy: Nucleus parasympathetic vagus nerve ), a core area in Myelencephalon (Mark brain ). The nerve cell bodies of the motor fibers are located in the motor nucleus of the vagus nerve (also nucleus ambiguus ) in the medullary brain.

The sensory fibers projecting from the periphery to the spinal trigeminal nucleus, and probably also to the nucleus pontine trigeminal nucleus, while the sensory fibers are routed to the nucleus of the solitary tract.

The nerve occurs in the region of the medulla oblongata in the sulcus retroolivaris side of Olive (together with accessory nerve and glossopharyngeal nerve, lower triad ) to the brain surface and pulls, like the other nerves of the Vagusgruppe, through the jugular foramen of the skull capsule. Here he passes through two closely adjacent ganglia:

• The superior ganglion ( jugular ganglion also, in animals ganglion proximal ): still within the cranial cavity or in the jugular foramen
• The inferior ganglion ( nodose ganglion also, in animals ganglion distal ): outside the cranial cavity

In both of these ganglia, the somata of afferent fibers are (a distinction between sensitive and sensory is no longer made ​​) of the vagus nerve.

Course outside the skull

The vagus nerve in the neck pulls together with the common carotid artery and the internal jugular vein in a common connective tissue sheath, the carotid sheath, towards the chest cavity. With a good ultrasound machine can be the nerve in the area of the carotid arteries also locate sonographically. For most other mammals it is connected over the entire neck to the sympathetic trunk vagosympathicus.

At the thoracic inlet of the vagus nerve passes over the subclavian artery, while the left vagus nerve passes over the aortic arch. In the chest area of the vagus runs through the upper mediastinum, and later the posterior mediastinum.

There, right and left vagal esophageal store at ( esophagus ), which mix the fibers of both sides and form the esophageal plexus, but it as anterior vagal trunk ( from the left vagus nerve in animals: the ventral vagal trunk ) and vagal trunk posterior ( from the right vagus nerve in animals: dorsal vagal trunk ) get together with the esophagus through the diaphragm through the esophageal hiatus into the abdomen.

Ramifications of the vagus nerve

Ramus meningeus

The meningeal ramus ( Hirnhautast ) pulls back through the jugular foramen into the cranial capsule to innervate the dura mater of the posterior fossa ( posterior fossa ). He also innervates the occipital sinus and the transverse sinus sensitive.

Auricular branch

The auricular branch ( Ohrast ) runs through the mastoid canaliculus and the petrotympanic fissure. It supplies the sensitive skin of the inner side of the auricle and the external auditory canal and a part of the eardrum.

The branch is responsible for ensuring that may occur with irritation of the outer ear canal (foreign bodies, rinsing with cold water) vegetative symptoms such as coughing or vomiting.

Rami pharyngei

The Rami pharyngeal ( throat branches) draw the pharyngeal plexus. This is a plexus of vagus fibers, fibers of the glossopharyngeal nerve and cervical sympathetic fibers from the superior ganglion. Revenge branches supply the throat muscles and the soft palate and are of great importance for swallowing. They are therefore also responsible for the gag reflex and the swallowing reflex.

Ramus oesophageus

The Ramus oesophageus ( Speiseröhrenast ) provides motor innervation to the striated muscle of the esophagus.

Superior laryngeal nerve

The superior laryngeal nerve (upper laryngeal nerve, called with animals cranial laryngeal nerve ) passes from the inferior ganglion and extends to the larynx. His external branch supplies the cricothyroid muscle muscle, the inner mucous membrane of the larynx above the vocal folds sensitive. The superior laryngeal nerve guides the sensitive information that ensure the reflexive closure of the larynx in contact with liquids and for the cough reflex.

Depressor nerve

The depressor nerve does not occur in humans. In animals it originates at the front of the neck from the vagus and unites again shortly afterwards with him. At the thoracic inlet it separates again from the vagus and pulls to the aorta. He directs information from receptors in the aortic wall, which register the blood pressure ( baroreceptors ) to the brain stem. In humans, these fibers run in the cardiac branches of the vagus nerve itself

The nerve fibers provide, as well as the carotid sinus, for regulation of blood pressure.

Rami cardiaci

The Rami cardiaci ( cardiac branches) provide the parasympathetic influence on the heart activity. They convey a reduction in heart rate ( chronotropy right vagus ). On the force of contraction of the heart ( inotropy ), the vagus no effect as it merely the excitation transition from auricle to ventricle inhibits (left vagus ), but not innervates the heart muscles. Only the sympathetic nervous system increases the muscular power of the heart and thus has a positive inotropic ( gr ís, iNOS = strength, muscle ).

The recurrent laryngeal nerve

The recurrent laryngeal nerve ( declining laryngeal nerve, vocal nerve) supplies all laryngeal muscles except the cricothyroid muscle musculus as well as dining and trachea.

He has a great clinical significance (→ recurrent laryngeal nerve palsy ) through its special history and its important function.

Smaller chest branches

The Rami tracheal (windpipe branches) and Rami bronchales ( bronchial tubes ) form on the lung root, together with sympathetic fibers from the sympathetic trunk, the pulmonary plexus (lung shield). The sensitive fibers of the vagus nerve are the regulation of respiration and the cough reflex of great importance. The parasympathetic fibers trigger a narrowing of the bronchial tubes.

Rami oesophagei ( esophageal branches) supply the chest portion of the esophagus, Rami pericardial pericardium.

Abdominal branches

The via the vagal trunk anterior ( ventral ) and vagal trunk posterior ( dorsal ) pulling into the abdominal cavity fibers supply parasympathetic most of the abdominal organs (stomach, liver, kidney and small intestine) until and including the transverse colon (called Cannon -Böhm point). They also provide viszerosensible information.

Activity measurement

With the aid of heart -rate variability analysis is possible to make the activity of the vagal visible. After the detection of cardiac electrical activity ( ECG), and the frequency of analysis of the portion of the vagus nerve appears as curve peak in the heart frequency band (the actual heart rate is out of the figure to the right ). If the measurement in physical rest (about 60-80 beats / minute = 1.0 to 1.33 Hz) is the activity of the vagus in the frequency range from 0.15 to 0.4 Hz ( blue curve), ie, in the rhythm 3-7 heart beats. Increases the heart rate, also the activity of the vagus nerve in a higher frequency range shifts. During physical exertion ( maximum physical load ) is the maximum usually 0.7 to 1.1 Hz ( red curve).

Clinical references

Medicine

• Vagotomy ( severing of the nerve)
• Vagal tone ( increased activity of the nerve )
• Laryngeal - superior neuralgia ( neuralgia of the upper laryngeal nerve)
• Vagus nerve stimulator ( used in the treatment of epilepsy )

Veterinary Medicine

• Larynx pipes ( paralysis of the laryngeal nerve caudal )
• Hoflund syndrome (damage to the terminal branches of the nerves with vagal tone in the chest in ruminants )