ABSTRACT
The inside of the ventricular myocyte is negative mostly due to a slight deficit of potassium ions inside the cell. The key to understanding the genesis of a transmembrane potential is to realize that movement of very few ions across the sarcolemma is what is important; there is no measurable change in ion concentration inside or outside the myocyte. The inside of a myocyte is positive with respect to the outside at the peak of the action potential. Most of the positives and negatives interact as charge pairs to maintain electroneutrality. If every positive and negative ion were paired, the resting membrane potential would be zero. However, in resting ventricular muscle cells the electrical potential difference across the membrane, the resting transmembrane potential or resting potential, is about -80 to -90 mV. A ventricular muscle cell action potential develops in response to an adequate electrical stimulus.
