Nerve

Nerve
Nerves of the left upper extremity.gif
Nerves (yellow) in the arm
Details
SystemNervous system
Identifiers
Latinnervus
D010525
A14.2.00.013
65239 65132, 65239
Anatomical terms of neuroanatomy

A nerve is an enclosed, cable-like bundle of nerve fibres (called axons) 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. Each axon within the nerve is the tail of a neuron, and other supportive cells such as Schwann cells exist. Schwann cells that coat the axons in myelin.

Each nerve is a cordlike structure containing bundles of axons. 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.

In the central nervous system, the analogous structures are known as tracts.[1][2]

Structure

Cross-section of a nerve

Each nerve is covered on the outside by a dense sheath of connective tissue, the epineurium. Beneath 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 from the surface of the spinal cord to the level where 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 and often travel 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.

Categories

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

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

Other Languages
Afrikaans: Senuwee
Alemannisch: Nerv
العربية: عصب
aragonés: Niervo
ܐܪܡܝܐ: ܓܝܕܐ
asturianu: Nerviu
авар: Нерв
azərbaycanca: Sinir
বাংলা: স্নায়ু
Bân-lâm-gú: Sîn-keng
башҡортса: Нерв
беларуская: Нерв
беларуская (тарашкевіца)‎: Нэрва
български: Нерв
bosanski: Živac
català: Nervi
čeština: Nerv
chiShona: Dzira (nhengo)
Cymraeg: Nerf
dansk: Nerve
Deutsch: Nerv
ދިވެހިބަސް: ފަތިނާރު
eesti: Närv
Ελληνικά: Νεύρο
español: Nervio
Esperanto: Nervo
euskara: Nerbio
فارسی: عصب محیطی
français: Nerf
Gaelg: Nearag
Gàidhlig: Leith
galego: Nervio
한국어: 신경
հայերեն: Նյարդ
हिन्दी: तंत्रिका
Ido: Nervo
Bahasa Indonesia: Saraf
interlingua: Nervo
íslenska: Taug
italiano: Nervo
עברית: עצב
ქართული: ნერვი
қазақша: Жүйкелер
Kiswahili: Neva
kurdî: Birik
Кыргызча: Нерв
лакку: Туниу
Latina: Nervus
latviešu: Nervs
lietuvių: Nervas
Lingua Franca Nova: Nervo
lumbaart: Nerv
македонски: Живец
മലയാളം: നാഡി
Bahasa Melayu: Saraf
Nederlands: Zenuw
日本語: 神経
norsk: Nerve
norsk nynorsk: Nerve
occitan: Nèrvi
oʻzbekcha/ўзбекча: Nerv
ਪੰਜਾਬੀ: ਤੰਤੂ
پښتو: رگ
polski: Nerw
português: Nervo
română: Nerv
Runa Simi: Ankucha
русский: Нерв
संस्कृतम्: नाडी
Scots: Nerve
Simple English: Nerve
slovenčina: Nerv
slovenščina: Živec
کوردی: دەمار
српски / srpski: Живац
srpskohrvatski / српскохрватски: Živac
suomi: Hermo
svenska: Nerv
தமிழ்: நரம்பு
తెలుగు: నాడి
Türkçe: Sinir
українська: Нерв
اردو: عصب
Tiếng Việt: Dây thần kinh
文言: 細筋
Winaray: Nerve
吴语: 神经
ייִדיש: נערוו
粵語: 神經線
中文: 神经