This MedLibrary.org supplementary page on End-plate potential is provided directly from the open source Wikipedia as a service to our readers. Please see the note below on authorship of this content, as well as the Wikipedia usage guidelines. To search for other content from our encyclopedia supplement, please use the form below:
Related Sponsors
End-plate potential
An end plate potential is the change in membrane potential induced by the action of multiple mini end plate potentials (MEPP).
In resting muscle, there is occasional leak of single acetylcholine vesicles. This produces a very small but notable electrical response in the muscle (~0.5mV). The response generated by one acetylcholine-containing vesicle represents the smallest possible depolarization which can be induced in a muscle ie. represents a MEPP.
If multiple vesicles are released, the electrical response is correspondingly larger. The summation of multiple MEPPs produces an End Plate Potential (EPP).
In a normal muscular contraction, ~150 acetylcholine vesicles are released. Therefore, the EPP is 150 times greater than the MEPP.[1]
Because the electrical depolarization of a muscle must be an integer multiple of the MEPP, muscle depolarization is considered quantal.
Stated another way: because you cannot have 0.5 of a vesicle released (ie the vesicle contents are completely exocytosed or not at all), the depolarization of a muscle must be a multiple of the depolarization caused by one single vesicle being exocytosed.
Pathological correlates:
(1) Myasthenia Gravis : In Myasthenia Gravis, there is autoimmune destruction of post synaptic acetylcholine receptors. Because there are less receptors, it is less probable that all the acetylcholine within a vesicle will find a receptor to bind to. Consequently, MEPP is decreased in myasthenia. As EPP is the summation of MEPPs, it is also decreased.
(2) Lambert Eaton Syndrome: In Lambert Eaton syndrome, presynaptic calcium channels responsible for facilitating vesicle exocytosis are subject to autoimmune destruction. Because less calcium influx occurs, less vesicles are exocytosed. The MEPP remains identical to a normal person because once a vesicle is released, its effect on the post-synaptic receptors is not affected by the disease. However, the EPP is lower relative to normal because less vesicles are able to be released.
- See main article: Postsynaptic potential.
See also
 |
This neuroscience article is a stub. You can help Wikipedia by expanding it. |
Wikipedia content modification information:
- This page was last modified on 21 September 2008, at 21:37.
Wikipedia Authorship and Review
Wikipedia content provided here is not reviewed directly by MedLibrary.org. Wikipedia content is authored by an open community of volunteers and is not produced by or in any way affiliated with MedLibrary.org.
Wikipedia Usage Guidelines
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "End-plate potential".
The URL for this specific entry is:
All Wikipedia text is available under the terms of the GNU Free Documentation License. (See Copyrights for details). Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc.