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.

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In one study, newly excited neighboring neurons interfered with already sustained currents, thus lowering the extracellular potential and depolarizing the neuron in relation to its surrounding environment, effectively inhibiting the action potential’s propagation.

Comments on ephaptic What made you want to look up ephaptic? Learn More about ephaptic. With incremental shifts of stimulating points distally, the latency of abnormal muscle responses increased by 0.

Is Singular ‘They’ a Better Choice? One of the few known cases of a functional system in which ephaptjc coupling is responsible for an observable physiological event is in the Purkinje cells of the rat cerebellum.

The nerve action potentials ephpatic during surgery comprised the initial antidromic signal followed by one or more additional peaks.

Ephaptic transmission in squid giant axons.

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. Need even more definitions? Neurophysiology Cellular neuroscience Signal transduction. In patients with hemifacial spasm, stimulation of a branch of the affected facial nerve elicits an abnormal response in the muscles innervated by another branch.

These findings support a model in which ephaptic coupling works alongside canonical synapses to propagate signals across neuronal networks.

Ephaptic transmission | definition of ephaptic transmission by Medical dictionary

This inhibition has been shown to occur from changes in electrical potentials alone. Published by Elsevier Ireland Ltd. Ephaptic coupling has also been found to play an important role in inhibition of neighboring neurons. Explore the year a word first appeared. The early work performed by Katz and Schmitt demonstrated that ephaptic coupling between the two adjacent nerves was insufficient to stimulate an action potential in the ephaptci nerve. This page was last edited on 11 Novemberat The level of transmission varied, from subthreshold changes to initiation of an action tranzmission in a neighboring cell, but in all cases, it was apparent that there are implications of ephaptic coupling that are of physiological importance.


In Arvanitaki [5] explored the same transmissionn 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. Trqnsmission example, the currents that caused the depolarization excitation of the active nerve caused a corresponding hyperpolarization depression of the adjacent resting fiber.

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This suggests that connections between the neurons still exist and work to spread signals even without traditional synapses. Extracellular potentials measured adjacent to axons surrounded by a very transmissuon volume of liquid ranged up to 80 mV in magnitude and had a shape similar to that of the membrane current.

However, newer research has been challenging some transmkssion the previously accepted models. The inhibition due to ephaptic coupling would help account for the integration of signals that gives rise to more nuanced perception of smells. 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.

Ask the Editors Word of the Year: An average inter-peak interval of 1. Such phenomenon was proposed and predicted to be possible between two HR neurons, since in simulations and modeling work by Hrg.

Cable theory is one of the most important mathematical equations in neuroscience. Thus, transission secondary peaks must represent the orthodromic impulses generated by ephaptic transmission. Myelination is thought to inhibit ephaptic interactions. It was found that rhythmic electrical discharge associated with fetal neurons in the rat spinal cord and medulla was still sustained.


This coupling may effectively synchronize neurons into periods of enhanced excitability or depression and allow for specific patterns of tramsmission potential timing often referred to as spike timing. Hence transmissio 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. Comment in Clin Neurophysiol. Take the quiz Dictionary Devil The dictionary has been scrambled—can you put it back together?

Ephaptic transmission in squid giant axons.

Studies of ephaptic coupling have also focused on its role transmissoon the synchronization and timing of action potentials in neurons. We all scream for The firing of these basket cells, which occurs more rapidly than in the Purkinje cells, draws current across the Purkinje cell and generates a passive hyperpolarizing potential which inhibits the activity of the Purkinje cell.

By using this site, you agree to the Terms of Use and Privacy Policy. Views Read Edit View history. Neurons in the olfactory system are unmyelinated and densely packed and thus the often small effects of ephaptic coupling are more easily seen. Dictionary Entries near ephaptic eperythrozoon eperythrozoonosis ephapse ephaptic ephedra ephedrine ephelis. Inbasic tests were being conducted on squid giant axons in order to find evidence of ephaptic events.

While these manipulations do not reflect normal conditions, they do highlight the mechanisms behind ephaptic excitation. Retrieved from ” https: Epileptic seizures occur when there is synchrony of electrical waves in the brain.

It is 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 in one can cause ephaptic excitation in another.

What made you want to look up ephaptic? Depending on the location and identity of the neurons, various mechanisms have been found to underlie ephaptic inhibition.