5. What are the structural and functional differences between cardiac myocardial (contractile) cells and autorhythmic cells? What are intercalated discs and what is their primary function? 6. Review the concept of excitation-contraction coupling. Compare excitation-contraction coupling for a skeletal muscle fiber and a cardiac myocardial contractile cell. Why does "excitation" look different for myocardial cells? Pay attention to the types of channels found in myocardial cells and ion flux, specifically the role of calcium.