This video deals with excitation contraction coupling of cardiac muscles and how it interrelates with skeletal muscles action. Activation of ryanodine receptors, and action of calcium on troponin and tropomyosin is also discussed Process of cardiac muscle cell relaxation is also discussed. Timeline 0:00 Introduction 0:24 Entrance of nervous impulse 0:55 Action of sodium on pacemaker cells 1:57 Encounter of action potential with calcium receptors 2:57 Ryanodine receptors 4:07 Action of calcium on troponin and tropomyosin 5:26 Process of relaxation of cardiac muscle