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The action potential and nervous conduction

Fry, CH and Jabr, RI (2010) The action potential and nervous conduction Surgery, 28 (2). 49 - 54. ISSN 0263-9319

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Abstract

An actionpotential is a transient depolarization of the membrane potential of excitable cells. They serve two main functions: to transmit and encode information, and to initiate cellular events such as muscular contraction. In this article actionpotentials generated in nerves will be the focus of attention. An actionpotential results from a transient change to the properties of the cell membrane, from a state where it is much more permeable to K+ than Na+, to a reversal of these permeability properties. Thus during the actionpotential an influx of Na+ is responsible for the rapid depolarization and an efflux of K+ causes repolarization. This ionic basis of the actionpotential can be predicted from the Nernst equation and is illustrated in the text. Changes to membrane ionic permeability are due to the opening and closing of voltage-gated ion channels, and the properties of such channels explain additional phenomena such as refractoriness, threshold and cellular excitability. Actionpotentials conduct with a finite velocity along nerve axons, and the actual velocity depends on a number of factors that include: fibre radius, temperature, functional ion channel number and the presence of a myelin sheath. The physical basis of conduction is explained by the local circuit hypothesis. Synaptic transmission of an actionpotential is explained in terms of excitatory post-synaptic potential (EPSP) generation at the post-synaptic membrane. The facility by which post-synaptic actionpotential may be developed is explained in terms of temporal and spatial summation as well as the influence of inhibitory transmitters.

Item Type: Article
Additional Information: NOTICE: this is the author’s version of a work that was accepted for publication in Surgery. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Surgery, 28(2), February 2010, DOI 10.1016/j.mpsur.2009.12.00.
Divisions: Faculty of Health and Medical Sciences > Biochemistry and Physiology
Depositing User: Symplectic Elements
Date Deposited: 09 May 2012 13:14
Last Modified: 23 Sep 2013 19:17
URI: http://epubs.surrey.ac.uk/id/eprint/285513

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