Question 1: What happened to the active force when you increased the length of the strip of toad ventricular muscle? Why did this happen? In your answer, consider the interactions between actin and myosin molecules in the cardiac muscle that underlie your observations.
Question 2: Briefly describe the significance of this length-force relation to the function of the whole heart.
Question 3: What happened to the contraction strength of the strip of cardiac muscle when you increased the concentration of calcium in the bath? How can you account for this effect? In your answer consider how extracellular calcium concentration affects cytosolic calcium concentration during depolarisation of a cardiac muscle cell
Question 4: Explain how calcium interacts with the contractile machinery of the cardiac muscle cell to alter contractility
Question 5: Describe how the strength of contraction of the cardiac muscle strip was altered in the absence of oxygen. How can you account for this effect?
Question 6: What 'cardiovascular event' does this simulate?
Question 7: Describe the mechanism via which adrenaline modulates cardiac contractility.
Question 8: State what happened to the contraction strength of the strip of cardiac muscle when you added nifedipine to the bath. In terms of the process of excitation-contraction coupling, how can you explain the effect of nifedipine?
Question 9: What do we mean by the term 'cardiac contractility'? In your answer, consider both the mechanisms at the level of cross-bridge formation and how changes in contractility alter stroke volume in the intact heart.