“Potassium channels are the most widely distributed type of ion channel and are found in virtually all living organisms. They form potassium-selective pores that span cell membranes. Potassium channels are found in most cell types and control a wide variety of cell functions. Potassium channels function to conduct potassium ions down their electrochemical gradient, doing so both rapidly and selectively. Biologically, these channels act to set or reset the resting potential in many cells. In excitable cells, such asneurons, the delayed counterflow of potassium ions shapes the action potential. By contributing to the regulation of the action potential duration in cardiac muscle, malfunction of potassium channels may cause life-threatening arrhythmias. Potassium channels may also be involved in maintaining vascular tone.”