WordNet

any bundle of nerve fibers running to various organs and tissues of the body (同)nervus
a qualified accountant who inspects the accounting records and practices of a business or other organization
a student who attends a course but does not take it for credit
of or relating to the process of hearing; "auditory processing"; "an audile person" (同)audile, auditive
control of your emotions; "this kind of tension is not good for my nerves"

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〈C〉『神経』 / 〈C〉《複数形で》『神経過敏』,いらだち / 〈U〉『勇気』,度胸(courage) / 〈U〉《時にa ~》厚かましさ,ずぶとさ;無礼 / 〈C〉葉脈;(昆虫の)翅脈(しみゃく) / 〈人,特に自分〉‘に'力を与える,‘を'元気づける
《まれ》聞き手,傍聴人 / 会計検査官,監査役 / 《米》(大学で単位を取らない)聴講生
耳の,聴覚の

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/05/07 21:23:54」(JST)

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^[1]

The cochlear nerve (also auditory or acoustic nerve) is one of two parts of the vestibulocochlear nerve, a cranial nerve present in higher vertebrates. The cochlear nerve carries sound waves from the cochlea of the inner ear directly to the brain. The other portion of the vestibulocochlear nerve is the vestibular nerve, which carries spatial orientation information to the brain from the semicircular canals.

Anatomy and connections

In terms of their anatomy, auditory nerve fibers are bipolar, with the most distal portion being called the peripheral process and the central projection being called the axon; these two projections are also known as the "peripheral axon" and the "central axon". The peripheral process is sometimes referred to as a dendrite, although that term is somewhat inaccurate. Unlike the typical dendrite, the peripheral process generates and conducts action potentials, which then "jump" across the cell body (or somata) and continue to propagate along the central axon. In this respect, auditory nerve fibers are somewhat unique bipolar cells in that action potentials pass through the soma. Both the peripheral process and the axon are myelinated.

In humans, the number of nerve fibers within the cochlear nerve averages around 30,000.^[2] The number of fibers varies significantly across species for example; the domestic cat has some 50,000 fibers. Auditory nerve fibers provide synaptic connections between the hair cells of the cochlea and the cochlear nucleus within the brain-stem. The cell bodies of the cochlear nerve lie within the central aspect of the cochlea and are collectively known as the spiral ganglion. This name reflects the fact that the cell bodies, considered as a unit, have a spiral (or perhaps more accurately, a helical) shape, reflecting the shape of the cochlea. The terms "cochlear nerve fiber" and "spiral ganglion cell" are used, to some degree, interchangeably, although the former may be used to more specifically refer to the central axons of the cochlear nerve. These central axons exit the cochlea at its base, where it forms a nerve trunk. In humans, this aspect of the nerve is roughly one inch in length. It projects centrally to the brain-stem, where its fibers synapse with the cell bodies of the cochlear nucleus. A good anatomical description of human auditory nerve fibers is provided by Spoendlin and Schrott (1985). Important earlier work was done by Schuknecht.

It was once believed that most of the cochlear nerve fibers were directed to the outer hair cells, but it is now understood that at least 90% of the cochlear ganglion cells terminate on inner hair cells, the rest terminating on the outer hair cells.

The transmission between the inner hair cells and the neurons is chemical, using glutamate as a neurotransmitter.

Types of neurons

The cochlear neurons can be divided into two groups: Type I and Type II.

Type I neurons make up 90-95% of the neurons and innervate the inner hair cells. They have a relatively large diameter, and are bipolar and myelinated. Each type I axon innervates only a single hair cell, but each hair cell directs its output to an average of 10 nerve fibers
Type II cells, which have a relatively small diameter, connect with the outer hair cells, are mono-polar and are not myelinated.

Cochlear nuclear complex

The axons from each cochlear nerve terminate in the cochlear nuclear complex which are ipsilaterally located in the medulla of the brain-stem. The cochlear nucleus is the first 'relay station' of the auditory nervous system and receives mainly ipsilateral afferent input.

The three major components of the cochlear nuclear complex are: (see figure below)

the dorsal cochlear nucleus (DCN)
the anteroventral cochlear nucleus (AVCN)
the posteroventral cochlear nucleus (PVCN)

Each of the three cochlear nuclei are tonotopically organized. The axons from the lower frequency area of the cochlea innervate the ventral portion of the dorsal cochlear nucleus and the ventrolateral portions of the anteroventral cochlear nucleus, while the higher frequency axons project into the dorsal portion of the anteroventral cochlear nucleus and the uppermost dorsal portions of the dorsal cochlear nucleus. The mid frequency projections end up in between the two extremes, in this way the frequency spectrum is preserved.

References

^ osin
^ Spoendlin H, Schrott A (1989). "Analysis of the human auditory nerve". Hear Res 43 (1): 25–38. doi:10.1016/0378-5955(89)90056-7. PMID 2613564.

Additional images

Ear anatomy
Cochlear nucleus innervated by a branching auditory nerve fibre
Terminal nuclei of the vestibular nerve, with their upper connections.
Transverse section of the cochlear duct of a fetal cat.
Floor of ductus cochlearis.
Diagrammatic longitudinal section of the cochlea
Organ of corti

External links

Illustration at cytochemistry.net
Gray's page #1059

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

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English Journal

Opposing expression gradients of calcitonin-related polypeptide alpha (Calca/Cgrpα) and tyrosine hydroxylase (Th) in type II afferent neurons of the mouse cochlea.

Wu JS1,2, Vyas P2,3, Glowatzki E1,2,3, Fuchs PA1,2,3.
The Journal of comparative neurology.J Comp Neurol.2018 Feb 15;526(3):425-438. doi: 10.1002/cne.24341. Epub 2017 Nov 13.
PMID 29055051

Executive abilities in children with congenital visual impairment in mid-childhood.

Bathelt J1, de Haan M2, Salt A3, Dale NJ3,4.
Child neuropsychology : a journal on normal and abnormal development in childhood and adolescence.Child Neuropsychol.2018 Feb;24(2):184-202. doi: 10.1080/09297049.2016.1240158. Epub 2016 Nov 3.
PMID 27809665

Pure-Tone Masking Patterns for Monopolar and Phantom Electrical Stimulation in Cochlear Implants.

Saoji AA1, Koka K, Litvak LM, Finley CC.
Ear and hearing.Ear Hear.2018 Jan/Feb;39(1):124-130. doi: 10.1097/AUD.0000000000000471.
PMID 28700446

Japanese Journal

聴覚機能マップ (増大特集ブロードマン領野の現在地)

Brain and nerve
NAID 40021190819

Current Status and Problems Associated with Tinnitus Treatment at Municipal Hospitals

耳鼻咽喉科臨床　補冊 151(0), 4-5, 2017
NAID 130006235233

内耳道内に発生した前下小脳動脈遠位部動脈瘤破裂の1例

脳神経外科ジャーナル 26(9), 682-687, 2017
NAID 130006100285

Related Pictures

★リンクテーブル★

リンク元	「聴神経」「octaval」
関連記事	「nerve」「auditory」

「聴神経」

Nerve: Cochlear nerve
	Diagrammatic longitudinal section of the cochlea. (Cochlear nerve is in center, shown as striped.)
	Part of the cochlear division of the acoustic nerve, highly magnified.
Latin	nervus cochlearis
Gray's	p.906
From	Vestibulocochlear nerve
MeSH	Cochlear+Nerve