Vestibulocochlear nerve

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Selected structures of the middle and inner ear with cranial nerves VII and VIII.
1 Vestibular nerve
2 Cochlear nerve
3 Facial nerve
4 Outer facial knee with Ggl. geniculi
5 chorda tympani
6 cochlea
7 semicircular canals
8 hammer handle
9 eardrum
10 eustachian tube

The paired vestibulocochlear nerve (from the Latin vestibulum “atrium” [for the vestibular organ ] and cochlea “cochlea ” [for the cochlea ]), also called the eighth cranial nerve , N. VIII , carries sensory (especially somato afferent ) fibers from the inner ear . It is the auditory and equilibrium nerve , formerly also known as the statoacusticus nerve , and consists of two parts:

  • The vestibular nerve ( staticus ) is the equilibrium nerve ,
  • the cochlear nerve ( acousticus ) the auditory nerve.

The nerves carry the afferent information from the respective receptor areas in the inner ear to the brain . In addition, there are also efferent tracts that allow fine-tuning of the hearing in the auditory nerve.

Vestibular nerve

The vestibular nerve (obsolete static nerve ) is the equilibrium nerve . The cell bodies of the bipolar nerve cells of the nerve are located in the vestibular ganglion ( Scarpa ganglion ). This ganglion consists of two distinct subdivisions and lies at the bottom of the internal auditory canal ( Meatus acousticus internus ). The nerve cell processes (afferent and efferent) pull to the receptor areas of the equilibrium part of the inner ear . A distinction is made between several nerve cords:

  • Nervus utriculoampullaris : to the macula utriculi and ampulla membranacea anterior and lateralis
  • Utricular nerve : to the macula utriculi
  • Nervus ampullaris anterior : to the ampulla membranacea anterior
  • Nervus ampullaris lateralis : to the ampulla membranacea lateralis
  • Nervus ampullaris posterior : to the ampulla membranacea posterior
  • Saccular nerve : to the macula sacculi

From the vestibular ganglion, all fibers of these nerves leading to the brain run as a uniform vestibular nerve into the cranial cavity . The fibers of the auditory nerve accumulate, creating the vestibulocochlear nerve.

The Vestibularanteile occur most trapezoidal body ( trapezoid body in the) hindbrain one. They mainly end in the four vestibular nuclei (vestibular or equilibrium nuclei ):

  • Nucleus vestibularis medialis ,
  • Nucleus vestibularis lateralis ,
  • Nucleus vestibularis superior and
  • Inferior vestibular nucleus

These nuclei are located in the hindbrain , and in some mammals also in the medullary brain . Some fibers run directly into the cerebellum and the reticular format . In the equilibrium nuclei, the first switch to the second neurons takes place, which have connections to almost all brain areas and the spinal cord and ensure a coupling of the balance information with other body functions.

Cochlear nerve

The cochlear nerve (more rarely the acoustic nerve ) is the auditory nerve. The nerve cell bodies of the bipolar nerve cells of the auditory nerve are located in the spiral ganglion ( cochleare ganglion ). This ganglion lies in a cavity in the center of the spiral coils . The extensions of these nerve cells attract the hair cells of the organ of Corti .

The axons of the nerve cells combine to form the cochlear nerve ( acousticus ) and attach to the inner auditory canal of the equilibrium nerve to the vestibulocochlear nerve. The auditory fibers end at the two auditory nuclei - the ventral cochlear nucleus and the dorsal cochlear nucleus - in the myelencephalon . Of these Hörkernen there are numerous connections to other brain sections via the auditory pathway to the auditory cortex ( Heschl transverse gyrus ) in the cerebrum reach.

Examination options for the function of the auditory nerve are the promontorial test and the auditory canal electrical stimulation .

literature

  • Martin Trepel: Neuroanatomy. Structure and function. 3rd, revised edition. Urban & Fischer, Munich et al. 2004, ISBN 3-437-41297-3 .
  • Franz-Viktor Salomon: nervous system, systema nervosum . In: Franz-Viktor Salomon, Hans Geyer, Uwe Gille (Ed.): Anatomy for veterinary medicine. Enke, Stuttgart 2005, ISBN 3-8304-1007-7 , pp. 464-577.