Cranial nerve VIII:
The vestibulocochlear nerve (also known as the auditory or acoustic nerve) is the eighth of twelve cranial nerves, and is responsible for transmitting sound and equilibrium (balance) information from the inner ear to the brain.
[edit] Structure
This is the nerve along which the sensory cells (the hair cells) of the inner ear transmit information to the brain. It consists of the cochlear nerve, carrying information about hearing, and the vestibular nerve, carrying information about balance. It emerges from the medulla oblongata and enters the inner skull via the internal acoustic meatus (or internal auditory meatus) in the temporal bone, along with the facial nerve.
[edit] Functions
The eighth cranial nerve has two prime roles. It is needed to convey information of vestibular sensation - that is, the position and movement of the head. Secondly, it is used for hearing.
[edit] Innervations
The nerve splits into two large divisions - the cochlear nerve and the vestibular nerve. Broadly speaking, the cochlear nerve innervates the cochlea, while the vestibular nerve goes to the vestibular apparatus.
[edit] Physiology
How sound information is coded on the cochlear nerve has long been a matter of scientific debate between two competing theories, a place theory and a temporal theory.
[edit] Symptoms of damage
vertigo, false sense of motion, loss of equilibrium (dark places), nystagmus, motion sickness
Some older texts call the nerve the acoustic or auditory nerve [1], but these terms have fallen out of widespread use because they fail to recognize the nerve's role in the vestibular system. Vestibulocochlear nerve is therefore preferred by most.
[edit] Additional images
Superficial dissection of brain-stem. Ventral view.
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Dissection showing the projection fibers of the cerebellum.
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Hind- and mid-brains; postero-lateral view.
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Upper part of medulla spinalis and hind- and mid-brains; posterior aspect, exposed in situ.
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Position of the right bony labyrinth of the ear in the skull, viewed from above.
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[edit] External links
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Nerves of head and neck: the cranial nerves and nuclei |
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| olfactory (AON->I) |
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| optic (LGN->II) |
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| oculomotor (ON,EWN->III) |
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| trochlear (TN->IV) |
no significant branches
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| trigeminal (PSN,TSN,MN,TMN->V) |
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| abducens (AN->VI) |
no significant branches
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| facial (FMN,SN,SSN->VII) |
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| vestibulocochlear (VN,CN->VIII) |
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| glossopharyngeal (NA,ISN,SN->IX) |
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| vagus (NA,DNVN,SN->X) |
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| accessory (NA,SAN->XI) |
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| hypoglossal (HN->XII) |
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