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Encyclopedia > Nodes of Ranvier
Nodes of Ranvier
Diagram of longitudinal sections of medullated nerve fibers.
Medullated nerve fibers stained with silver nitrate.
Gray's subject #183 727
MeSH Ranvier's+Nodes
Dorlands/Elsevier n_09/12575236
This article is about anatomy; for the musical group see Nodes of Ranvier (band)

Nodes of Ranvier are regularly spaced gaps in the myelin sheath around an axon or nerve fiber. About one micrometer in length, these gaps expose the axonal membrane to the extracellular fluid. (The myelin sheath is the fatty tissue layer coating the axon.) Image File history File links Gray631. ... Image File history File links Gray634. ... Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. ... Elseviers logo. ... Anatomical drawing of the human muscles from the Encyclopédie. ... Nodes of Ranvier formed in the fall of 2000. ... In neuroscience, myelin is an electrically insulating fatty layer that surrounds the axons of many neurons, especially those in the peripheral nervous system. ... An axon or nerve fiber, is a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neurons cell body or soma. ... A micrometre (American spelling: micrometer, symbol µm) is an SI unit of length equal to one millionth of a metre, or about a tenth of the size of a droplet of mist or fog. ... Lipids are a class of hydrocarbon-containing organic compounds. ... An axon or nerve fiber, is a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neurons cell body or soma. ...

Contents

Function in action potentials

The myelin sheath helps speed the neural impulse by insulating the electrical current and making it possible for the impulse to jump from node to node, a process known as saltatory conduction, as opposed to traveling down the axon in tiny increments. In electricity, current is the rate of flow of charges, usually through a metal wire or some other electrical conductor. ... Saltatory conduction is a means by which action potentials are transmitted along myelinated nerve fibers. ...


An action potential is the sharp electrochemical response of a stimulated neuron, a neuron whose membrane potential has been changed by a nearby cell, cells, or an experimentor. In an action potential, the cell membrane potential changes drastically and quickly as ions flow in or out of the cell. The action potential "travels" from one place in the cell to another, but ion flow occurs only at the nodes of Ranvier. Therefore, the action potential signal "jumps" along the axon, from node to node, rather than propagating smoothly, as they do in axons that lack a myelin sheath. This is due to clustering of voltage-gated Na+ and K+ ion channels at the Nodes of Ranvier. A. A schematic view of an idealized action potential illustrates its various phases as the action potential passes a point on a cell membrane. ... This article or section is in need of attention from an expert on the subject. ... International safety symbol Caution, risk of electric shock (ISO 3864), colloquially known as high voltage symbol. ... Ion channels are pore-forming proteins that help to establish and control the small voltage gradient that exists across the plasma membrane of all living cells (see cell potential) by allowing the flow of ions down their electrochemical gradient. ...


Unmyelinated axons do not have Nodes of Ranvier; voltage gated ion channels in these axons are considerably less ordered and spread over the entire membrane surface.


History

The myelin sheath and the nodes were discovered by French pathologist and anatomist Louis-Antoine Ranvier (1835-1922). To meet Wikipedias quality standards, this article or section may require cleanup. ... Greek anatome, from ana-temnein, to cut up), is the branch of biology that deals with the structure and organization of living things; thus there is animal anatomy (zootomy) and plant anatomy (phytonomy). ... Louis-Antoine Ranvier (b. ...


See also

The portion of nerve fiber between two Nodes of Ranvier is called an internodal segment (or internode). ...

External links


  Results from FactBites:
 
Louis-Antoine Ranvier (www.whonamedit.com) (0 words)
A node of Ranvier is a constriction in the myelin sheath that encases nerve fibres, occurring at more or less regular intervals along their length.
Ranvier made his lodgings there into a small histology laboratory, which in 1872 was annexed to Bernard's chair of experimental medicine and given official recognition as the Laboratoire d’Histologie of the École des Hautes Études.
Ranvier's dynamic way of approaching the study of microscopic anatomy made his laboratories a world centre for students of histology.
PERFORMANCE CHARACTERISTICS of the NODE OF RANVIER (576 words)
In the case of the Node of Ranvier as an example, all of the electrical characteristics associated with this feature can be provided based on the circuit model, shown in frame A above, when the Activa, shown as a rectangle, is replace with its symbolic equivalent.
The Activa of a Node of Ranvier is operated in a switching mode.
By overlaying these theoretical curves and delays on the published data, it is possible to determine the value of the circuit elements associated with a Node of Ranvier.
  More results at FactBites »

 
 

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