WordNet

any bundle of nerve fibers running to various organs and tissues of the body (同)nervus
easily agitated; "a nervous addict"; "a nervous thoroughbred"
of or relating to the nervous system; "nervous disease"; "neural disorder" (同)neural
of or relating to neurons; "neural network" (同)neuronal, neuronic
control of your emotions; "this kind of tension is not good for my nerves"

PrepTutorEJDIC

〈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
『神経の』 / 『神経質な』,神経過敏な / 『心配な』,不安な
神経[系統]の

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/10/13 02:48:35」(JST)

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Nerves (yellow) in the arm

A nerve is an enclosed, cable-like bundle of axons (the long, slender projections of neurons) in the peripheral nervous system. A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons to peripheral organs.

In the central nervous system, the analogous structures are known as tracts.^[1]^[2] Neurons are sometimes called nerve cells, though this term is potentially misleading since many neurons do not form nerves, and nerves also include non-neuronal Schwann cells that coat the axons in myelin.

Each nerve is a cordlike structure that contains many axons, also called nerve fibres. Within a nerve, each axon is surrounded by a layer of connective tissue called the endoneurium. The axons are bundled together into groups called fascicles, and each fascicle is wrapped in a layer of connective tissue called the perineurium. Finally, the entire nerve is wrapped in a layer of connective tissue called the epineurium.

Anatomy

Nerves are categorized into three groups based on the direction that signals are conducted:

Afferent nerves conduct signals from sensory neurons to the central nervous system, for example from the mechanoreceptors in skin.
Efferent nerves conduct signals from the central nervous system along motor neurons to their target muscles and glands.
Mixed nerves contain both afferent and efferent axons, and thus conduct both incoming sensory information and outgoing muscle commands in the same bundle.

Nerves can be categorized into two groups based on where they connect to the central nervous system:

Spinal nerves innervate much of the body, and connect through the spinal column to the spinal cord. They are given letter-number designations according to the vertebra through which they connect to the spinal column.
Cranial nerves innervate parts of the head, and connect directly to the brain (especially to the brainstem). They are typically assigned Roman numerals from 1 to 12, although cranial nerve zero is sometimes included. In addition, cranial nerves have descriptive names.

Cross-section of a nerve

Each nerve is covered externally by a dense sheath of connective tissue, the epineurium. Underlying this is a layer of flat cells, the perineurium, which forms a complete sleeve around a bundle of axons. Perineurial septae extend into the nerve and subdivide it into several bundles of fibres. Surrounding each such fibre is the endoneurium. This forms an unbroken tube which extends from the surface of the spinal cord to the level at which the axon synapses with its muscle fibres, or ends in sensory receptors. The endoneurium consists of an inner sleeve of material called the glycocalyx and an outer, delicate, meshwork of collagen fibres.^[2] Nerves are bundled along with blood vessels, since the neurons of a nerve have fairly high energy requirements.

Within the endoneurium, the individual nerve fibres are surrounded by a low protein liquid called endoneurial fluid. This acts in a similar way to the cerebrospinal fluid in the central nervous system and constitutes a blood-nerve barrier similar to the blood-brain barrier.^[3] Molecules are thereby prevented from crossing the blood into the endoneurial fluid. During the development of nerve edema from nerve irritation or (injury), the amount of endoneurial fluid may increase at the site of irritation. This increase in fluid can be visualized using magnetic resonance neurography, and thus MR neurography can identify nerve irritation and/or injury.

Physiology

A nerve conveys information in the form of electrochemical impulses (known as nerve impulses or action potentials) carried by the individual neurons that make up the nerve. These impulses are extremely fast, with some myelinated neurons conducting at speeds up to 120 m/s. The impulses travel from one neuron to another by crossing a synapse, the message is converted from electrical to chemical and then back to electrical.^[1]^[2]

Nerves can be categorized into two groups based on function:

Sensory nerves conduct sensory information from their receptors to the central nervous system, where the information is then processed. Thus they are synonymous with afferent nerves.
Motor nerves conduct signals from the central nervous system to muscles. Thus they are synonymous with efferent nerves.^[1]^[2]

Clinical significance

Micrograph demonstrating perineural invasion of prostate cancer. H&E stain.

Cancer can spread by invading the spaces around nerves. This is particularly common in head and neck cancer, and prostate and colorectal cancer.

Nerves can be damaged by physical injury as well as that of carpal tunnel syndrome and repetitive strain injury. Autoimmune diseases such as Guillain-Barré syndrome, neurodegenerative diseases, polyneuropathy, infection, neuritis, diabetes or failure of the blood vessels surrounding the nerve can all cause nerve damage which can vary in severity.

Multiple sclerosis is a disease associated with extensive nerve damage. It occurs when the macrophages of an individual's own immune system damage the myelin sheaths that insulate the axon of the nerve.

A pinched nerve occurs when pressure is placed on a nerve, usually from swelling due to an injury, or pregnancy and can result in pain, weakness, numbness or paralysis. Symptoms may be felt in areas far from the actual site of damage, a phenomenon called referred pain. Referred pain can happen when the damage causes altered signalling to other areas.

Neurologists usually diagnose disorders of the nerves by a physical examination, including the testing of reflexes, walking and other directed movements, muscle weakness, proprioception, and the sense of touch. This initial exam can be followed with tests such as nerve conduction study and electromyography (EMG).

Growth and stimulation

Nerve growth normally ends in adolescence, but can be re-stimulated with a molecular mechanism known as "Notch signaling."^[4]

References

Wikimedia Commons has media related to Nerves.

^ ^a ^b ^c Purves D, Augustine GJ, Fitzppatrick D et al. (2008). Neuroscience (4th ed.). Sinauer Associates. pp. 11–20. ISBN 978-0-87893-697-7.
^ ^a ^b ^c ^d Marieb EN, Hoehn K (2007). Human Anatomy & Physiology (7th ed.). Pearson. pp. 388–602. ISBN 0-8053-5909-5.
^ Kanda, T (Feb 2013). "Biology of the blood-nerve barrier and its alteration in immune mediated neuropathies". Neurol Neurosurg Psychiatry 84 (2): 208–212. PMID 23243216. |accessdate= requires |url= (help)
^ Yale Study Shows Way To Re-Stimulate Brain Cell Growth ScienceDaily (Oct. 22, 1999) — Results Could Boost Understanding Of Alzheimer's, Other Brain Disorders

UpToDate Contents

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1. 上肢末梢神経症候群の概要 overview of upper extremity peripheral nerve syndromes
2. 下肢末梢神経症候群の概要 overview of lower extremity peripheral nerve syndromes
3. 成人における詳細な神経学的検査 the detailed neurologic examination in adults
4. 臨床神経生理学 clinical neurophysiology
5. 神経伝導検査の概要 overview of nerve conduction studies

English Journal

Do high doses of AT1-receptor blockers attenuate central sympathetic outflow in humans with chronic heart failure?

Ruzicka M, Floras JS, McReynolds AJ, Coletta E, Haddad H, Davies R, Leenen FH.Source‡Division of Cardiology, University Health Network and Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada.
Clinical science (London, England : 1979).Clin Sci (Lond).2013 May 1;124(9):589-95. doi: 10.1042/CS20120437.
In patients with CHF (chronic heart failure) sympathetic activity increases as cardiac performance decreases and filling pressures increase. We hypothesized that in patients with mild-to-moderate CHF, higher than conventional doses of an AT1-receptor [AngII (angiotensin II) type 1 receptor] antagon
PMID 23163825

Evolutionary divergence of trigeminal nerve somatotopy in amniotes.

Rhinn M, Miyoshi K, Watanabe A, Kawaguchi M, Ito F, Kuratani S, Baker CV, Murakami Y, Rijli FM.SourceInstitut de Génétique et de Biologie Moléculaire et Cellulaire, UMR 7104, Strasbourg, France.
The Journal of comparative neurology.J Comp Neurol.2013 Apr 15;521(6):1378-94. doi: 10.1002/cne.23236.
The trigeminal circuit relays somatosensory input from the face into the central nervous system. In central nuclei, the spatial arrangement of neurons reproduces the physical distribution of peripheral receptors, thus generating a somatotopic facial map during development. In mice, the ophthalmic, m
PMID 23047619

Transcutaneous electrical nerve stimulation and placental vascularization in cases of uterine blood flow restriction.

de Oliveira Guimarães CS, Santos Tavares FC, Santos MN, Guimarães GC, Pacheco Olegário JG, Rocha LP, Reis LC, Dos Reis MA, da Cunha Castro EC, Miranda Corrêa RR.SourceDiscipline of General Pathology, Biological Sciences Department, Triângulo Mineiro Federal University , Uberaba , Brazil.
Fetal and pediatric pathology.Fetal Pediatr Pathol.2013 Apr;32(2):88-96. doi: 10.3109/15513815.2012.671648. Epub 2012 Apr 19.
Studies report transcutaneous electrical nerve stimulation (TENS) as a treatment for placental insufficiency. To induce utero-placental insufficiency in rats, the uterine artery was ligated. Transcutaneous electrical nerve stimulation was applied with a frequency of 80 Hz, pulse duration of 200 μs,
PMID 22515506

Japanese Journal

前立腺全摘除術後患者に対するMasturbation device : EGGの使用経験 : Penile rehabilitationとしての可能性

佐藤嘉一,丹田均,中嶋久雄,新田俊一,赤樫圭吾,半澤辰夫,戸邉武蔵,芳賀一徳,内田耕介,本間一也
泌尿器科紀要 59(5), 271-275, 2013-05-00
… Erectile dysfunction following radical prostatectomy (RP) is still a significant burden as a post-operative morbidity, despite advances in nerve-sparing techniques and penile (erectile function) rehabilitation (PR) programs. …
NAID 120005245089

A polylactic acid non-woven nerve conduit for facial nerve regeneration in rats

松峯元
東京女子医科大学雑誌 83(2), 120-121, 2013-04-25
NAID 120005302554

非侵襲自律神経疾患計測のための外乱に強い電子瞳孔計の開発(画像計測,<特集>医用画像論文)

鬼山将,彌冨仁,尾川浩一
電子情報通信学会論文誌. D, 情報・システム J96-D(4), 867-875, 2013-04-01
自律神経の働きを評価することにより,うつ病やアルツハイマー病らの病勢定量の可能性が示唆されている.自律神経機能を定量的に評価する手法として瞳孔反応検査法は,高い精度と信頼のおける被侵襲な手法として臨床応用されている.しかし,現在この検査で用いる瞳孔計は,瞳孔部の抽出を手動しきい値処理のみにより行っているため,測定中の患者の瞬きなどの要因により,瞳孔面積の正確な推移の計測が困難になる場合がある.そこ …
NAID 110009596334

Stereoscopic Three-Dimensional Images of an Anatomical Dissection of the Eyeball and Orbit for Educational Purposes

Matsuo Toshihiko,Takeda Yoshimasa,Ohtsuka Aiji
Acta Medica Okayama 67(2), 87-91, 2013-04-00
… The eyeball was dissected completely to observe the optic nerve and the ophthalmic artery. …
NAID 120005232497