Action potential: generation and propagation

Publication date: Available online 23 February 2016 Source:Anaesthesia & Intensive Care Medicine Author(s): Allan Fletcher In the normal resting state, the plasma membrane of nerve and muscle cells generates a transmembrane electrical potential difference – the intracellular surface of the membrane being approximately 70–80mV negative to the extracellular surface. This is a result of markedly different concentrations of ions inside and outside the cell, together with different membrane permeabilities to different ions that permits K+ ions to flow down their concentration gradient from inside to outside the cell. Nerve and muscle cells are ‘excitable’ because they can react to external stimuli by generating an extremely rapid change in transmembrane electrical potential difference known as the action potential. This comprises an initial explosive increase in membrane Na+ permeability that allows these ions to flood down their concentration gradient into the cell, thereby depolarizing the membrane such that the potential difference is transiently reversed to a positive value. However, in nerve and skeletal muscle this lasts for only a millisecond, at which time the membrane potential is just as rapidly restored to its resting negative value (repolarization). These events are controlled by the brief opening and closing of voltage-activated sodium and potassium channels in the membrane. The key features of the action potential are that it is: (1) an all-or-n...
Source: Anaesthesia and intensive care medicine - Category: Anesthesiology Source Type: research