3 - Ion Channels in Cardiac Muscle

Abstract

This chapter focuses on ion channels in cardiac muscle. Ion channels are the major transducers for communicating physiological signals within and between cells. At the cellular level, the formation of the heartbeat, as well as cardiac force development, are both directly regulated by the cardiac action potential, which depends on the coordinated actions of a large number of distinct sarcolemmal ion channels. At the subcellular level, the changes in membrane potential and flow of ions through sarcolemmal ion channels regulate ion channels in intracellular organelles, which determine contractile force by controlling Ca release from internal stores, and modulate energy production by the metabolic machinery in the cell. At the supercellular level, the staged activation sequence of the heart, progressing from the sinoatrial node to ventricle, is critically mediated by intercellular ion channels (connexons) that connect adjacent myocytes. This chapter discusses cardiac ion channels. It explains concepts related to autonomic regulation of cardiac action potential. It also describes formation and propagation of cardiac action potential. An overview of sarcolemmal ligand-gated ion channels is also presented. The chapter elaborates in detail about ion channels in intracellular organelles.