Physiology Which of the following is not true for cardiac and skeletal muscle fibers? A Both cardiac and skeletal muscles exhibit graded contraction B Excitation-contraction coupling in both depends upon increased intracellular Calcium C Excitation-contraction cdupling is not dependent on extracellular Ca2+ in skeletal muscle D Cardiac action potential has a plateau and a longer refractory period 💡 Explanation Which of the following is not true for cardiac and skeletal muscle fibers? ✓ Correct Answer: A. Both cardiac and skeletal muscles exhibit graded contraction