Infomation on the Vestibulocochlear Nerve, the Eighth Cranial Nerve

Infomation on the Vestibulocochlear Nerve, the Eighth Cranial Nerve
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Introduction

In the brain, there are twelve cranial nerves, which connect directly to the brain stem. The eighth cranial nerve is the vestibulocochlear nerve, also referred to as the auditory-vestibular nerve, since it is made up of two components. The vestibulocochlear enters the brain from the medulla oblongata, which is the lower part of the brain stem. The vestibulocochlear and facial nerves both travel through a canal in the temporal bone, called the internal auditory meatus.

The first part of the vestibulocochlear nerve, the vestibular nerve, detects balance from head and body motion. The second part of the vestibulocochlear, the cochlear nerve, receives auditory stimuli. The hair cells, or sensory cells, are responsible for transmitting the information from the inner ear to the brain. The vestibulocochlear nerve is also an afferent sensory nerve, meaning the nerve carries the information to the central nervous system, or CNS.

Mechanisms

An article in the “Seminars in Neurology” states that the vestibular nerve receives information from the semicircular canals (angular acceleration) and from the otolithic organs (linear acceleration). The Stritch School of Medicine elaborates that the vestibular apparatus detects movement through fluid vibration, which results in hair cell displacement. The vestibular nerve ends in the vestibular nuclear complex, which is found in the bottom of the fourth ventricle in the brain.

The cochlear nerve receives information from the organ of Corti, which the article in the “Seminars in Neurology” notes that the organ relays auditory information. The Stritch School of Medicine further explains that the cochlear duct has three bony ossicles, which “transduce sound waves into fluid movements in the cochlea.” The end of the cochlear nerve is found in the cochlear nucleus, which is located where the pons and medulla meets.

Consequences of Damage

The article in the “Seminars in Neurology” states that if damage occurs to either the nerves or the receptors that relay the essential information, hearing and equilibrium are affected. Examples of problems include disequilibrium, hearing loss, tinnitus, oscillopsia, otalgia and vertigo.