ABSTRACT
Repetitive and ordered cardiac contraction relies on a very precise sequence of events. It is the formation of an action potential that excites the individual cell. The sarcolemma of cardiac cells has a high-resistance, insulated phospholipid bilayer. Spaced throughout this layer are proteins that act as ion channels. Passage of ions through these channels alters the intracellular voltage potential, generating gradients with the extracellular environment.
