After reading this chapter you should be able to:

outline the ultrastructure and functions of the sarcomere, sarcoplasmic reticulum (SR), transverse tubules and gap junctions (3.2);

explain how the interactions between calcium (Ca²⁺), actin and myosin produce contraction (3.3);

sketch a ventricular action potential, label the various phases and name the ion channels responsible for each (3.6; 3.7);

explain the link between the action potential plateau and contractility (3.9);

describe Ca²⁺ cycling in cardiac myocytes and the factors affecting Ca²⁺ store size (3.9);

state the effect of diastolic length on contractile force (3.9; 3.10);

outline the effect of the following agents on contractile force: catecholamines; Ca²⁺ channel blockers; phosphodiesterase inhibitors; digoxin (3.8; 3.9);

draw and explain a delayed afterdepolarization (3.11).