Updated : Jan 13, 2020 in Medical


Some characteristics of ephaptic transmission of action potentials were investigated with squid giant axons. For these studies two isolated axons were placed. Thus, the secondary peaks must represent the orthodromic impulses generated by ephaptic transmission. An average inter-peak interval of ms between the. Ephaptic transmission was implied. NEUROLOGY (Ny) ; Aberrant conduction in human peripheral nerve: Ephaptic transmission? Richard A.

Author: Vigal Kazrakasa
Country: Estonia
Language: English (Spanish)
Genre: Marketing
Published (Last): 24 May 2016
Pages: 192
PDF File Size: 13.73 Mb
ePub File Size: 2.44 Mb
ISBN: 330-4-48854-664-2
Downloads: 67406
Price: Free* [*Free Regsitration Required]
Uploader: Narn

It may refer to the coupling of adjacent touching nerve fibers caused by the exchange of ions between the cells, or trasmission may refer to coupling of nerve fibers as a result of local electric fields.

However, many authors have worked to create more refined models in order to more accurately represent the environments of the nervous system.

Ephaptic transmission | definition of ephaptic transmission by Medical dictionary

Ephaptic coupling has also been found to play an important role in inhibition of neighboring neurons. Thus, the secondary peaks must represent the orthodromic impulses generated by ephaptic transmission. Although the exact functional role of this inhibition is still unclear, it may well have a synchronizing effect in the Purkinje cells as the ephaptic effect will limit the firing time. Literally How to use a word that literally drives some people nuts. While the idea of non-synaptic interactions between neurons has existed since the 19th century, there has historically been a lot of skepticism in the field of neuroscience.

Over time the term ephaptic coupling has come to be used not only in cases of electric interaction between adjacent elements, but also more generally to describe the effects induced by any field changes along the cell membrane. This coupling may effectively synchronize neurons into periods of enhanced excitability or depression and allow for specific patterns of action potential timing often referred to as spike timing.

Ephaptic transmission is the origin of the abnormal muscle response seen in hemifacial spasm.

Resources for ephaptic Time Traveler! For example, many authors have proposed models for cardiac tissue that includes additional variables that account for the unique structure and geometry of cardiac cells [14] varying scales of size, [19] or three-dimensional electrodiffusion.

Katz and Schmitt also observed that stimulation of both nerves could cause interference effects. When the speed of the propagated action potential is lowered by replacing the normal artifical seawater ASW with low-sodium ASW, some ephaptic effects are enhanced.


In intraoperative monitoring of 10 patients during microvascular decompression, we monitored propagating nerve action potentials with a handheld electrode placed on the facial nerve 3mm distal to the vascular compression site. Similarly, the currents that caused repolarization of the active nerve caused slight depolarization in the resting fiber. He’s making a quiz, and checking it twice Is Singular ‘They’ a Better Choice? More recent research, however, has focused on the more general case of electric fields that affect a variety of neurons.

Take the quiz Name That Thing Test your visual vocabulary with our question challenge!

ephaptic transmission

One study suggested that cortical cells represent an ideal place to observe ephaptic coupling due to the tight packing of axons, which allows for interactions between their electrical fields. In Arvanitaki [5] explored the same topic and proposed the usage of the term “ephapse” from the Greek ephapsis and meaning “to touch” to describe this phenomenon and distinguish it from synaptic transmission. Need transmissio more definitions?

For these studies two isolated axons were placed side by side or, on occasion, a single long axon was looped to form an “ephapse” between the axon trunk and one of its main branches. Inbasic tests were being conducted on squid giant axons in order to find evidence of ephaptic events. The nerve action potentials recorded during transmsision comprised the initial antidromic signal followed by one or more additional peaks.

Subscribe to America’s largest dictionary and get thousands more definitions and advanced search—ad free! Take the quiz Dictionary Devil The dictionary ephapti been scrambled—can you put it back together?

Comments on ephaptic What made you want to look up ephaptic? They tested the effects of changing extracellular transmiwsion which affects local electrical fields and found that one can block epileptic synchronization independent of chemical synapse manipulation simply by increasing the space between cells.

Test Your Knowledge – and learn some interesting things ephaltic the way. While these manipulations do not reflect normal conditions, they do highlight the mechanisms behind ephaptic excitation. It dphaptic concluded that in regions in which axons are confined by restricted extracellular volume, the large extracellular voltage changes arising during the passage of an action potential epphaptic one can cause ephaptic excitation in another.


This suggests that connections between the neurons still exist and work to spread signals even without traditional synapses. In a preoperative study of 21 patients, we delivered a series of stimuli, in short tdansmission, successively distally along the temporal branch of the facial nerve to record abnormal muscle responses from the orbicularis oculi and mentalis muscles.

These changes were attributed to the local currents that form the action potential. We tested the hypothesis that this anomaly results from lateral spread of impulses from one motor axon to another at the site of the nerve compression by the offending artery.

A hypothesis or explanation behind the mechanism is “one-way”, “master-slave”, or “unidirectional synchronization” effect as mathematical and fundamental property of non-linear dynamic systems oscillators like neurons to synchronize under certain criteria.

Dictionary Entries near ephaptic eperythrozoon eperythrozoonosis ephapse ephaptic ephedra ephedrine ephelis. The level of transmission varied, from subthreshold changes to initiation of an action potential in a neighboring cell, but in all cases, it was apparent that there are implications of ephaptic coupling that are of physiological importance. Published by Elsevier Ireland Ltd.

Get Word of the Day daily email! Hence the phenomenon is of not only fundamental interest but also applied one from treating epilepsy to novel learning systems.

This study establishes the mechanism of lateral spread responsible for abnormal muscle responses and contributes to the understanding trnasmission pathophysiology ephapyic hemifacial spasm.

It was found that rhythmic electrical discharge associated with fetal neurons in the rat spinal cord and medulla was still sustained. Early experiments, like those by du Bois-Reymond, [3] demonstrated that the firing of a primary nerve may induce the firing of an adjacent secondary nerve termed “secondary excitation”. The latter immediately abated, together with abnormal muscle responses, after microvascular decompression. Synchronization of neurons is in principle unwanted behavior, as brain would have zero information or be simply a transmizsion if all neurons would synchronize.

Hence it is a hypothesis that neurobiology and evolution of brain coped with ways of preventing such synchronous behavior on large scale, using it rather in other special cases. Neurophysiology Cellular neuroscience Signal transission.