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2.2 Cardiac Conduction — Test 1
Q1. Acetylcholine released by parasympathetic (vagal) nerves on heart pacemaker cells:✓ Binds a GPCR and activates a G protein to slow the heart rate
Q2. Purkinje fibres of the heart consist of specialised:✓ Cardiac muscle cells
Q3. The SA node, rather than the AV node, normally controls heart rhythm because:✓ The SA node depolarises spontaneously at the fastest rate
Q4. In a person with a heart rate of 72 beats per minute, the duration of one cardiac cycle is about:✓ 0.8 seconds
Q5. A cardiac cycle in a resting adult lasts approximately:✓ 0.8 seconds
Q6. In the synchronous contraction of cardiac muscle, electrical impulses pass directly from cell to cell through:✓ Gap junctions
Q7. Heart muscle normally cannot be tetanised because:✓ Its absolute refractory period is very long
Q8. Myocardial contractility is most closely correlated with the intracellular concentration of:✓ Calcium
Q9. The rhythmic beating of the heart is initiated by the:✓ Sinoatrial (SA) node
Q10. The T-wave of a normal ECG indicates:✓ Ventricular repolarisation
Q11. During each normal heartbeat the number of heart sounds typically produced is:✓ Two
Q12. The first heart sound of the cardiac cycle is caused by closure of the:✓ Mitral and tricuspid (AV) valves
2.2 Cardiac Conduction — Test 2
Q13. Stimulation of the vagus (parasympathetic) nerve affects the SA node by:✓ Slowing the rate of pacemaker depolarisation
Q14. Stimulation of the sympathetic cardiac nerves:✓ Increases the rate of SA node firing and heart rate
Q15. The pacemaker potential of SA-node cells depends on a slow inward current carried mainly by the:✓ 'Funny' (h) channels and calcium channels
Q16. In the cardiac conduction system, the normal pathway of the impulse is:✓ SA node → AV node → bundle of His → Purkinje fibres
Q17. The delay introduced at the AV node is important because it:✓ Allows the atria to finish emptying before ventricles contract
Q18. The P wave of the ECG represents:✓ Atrial depolarisation
Q19. The QRS complex of the ECG corresponds to:✓ Ventricular depolarisation
Q20. Cardiac muscle has an exceptionally long action potential plateau due to:✓ A sustained influx of calcium ions
Q21. Mayer waves seen in arterial blood pressure arise mainly from:✓ Rhythmic oscillations of the baroreceptor (vasomotor) reflex
Q22. Cardiac output is the product of:✓ Heart rate and stroke volume
Q23. During ventricular systole, the AV valves are ____ and the semilunar valves are ____:✓ Closed; open
Q24. The AV node can act as a secondary pacemaker; its intrinsic rate is:✓ Slower than the SA node (about 40–60 per minute)
2.2 Cardiac Conduction — Test 3
Q25. The natural pacemaker of the heart is the:✓ Sinoatrial (SA) node
Q26. The delay at the AV node allows time for the:✓ Atria to empty into the ventricles
Q27. The first heart sound ('lub') is produced by closure of the:✓ Atrioventricular valves
Q28. The conduction pathway after the AV node passes through the bundle of His and then the:✓ Purkinje fibres
Q29. Cardiac muscle cannot be tetanised because it has a:✓ Long absolute refractory period
Q30. The plateau phase of the cardiac action potential is due to:✓ A sustained calcium influx
Q31. Heart rate is slowed by stimulation of the:✓ Vagus (parasympathetic) nerve
Q32. Cardiac muscle cells are electrically connected so the heart contracts as a unit via:✓ Gap junctions in intercalated discs
Q33. During one cardiac cycle, the atria contract:✓ Before the ventricles
Q34. The second heart sound ('dub') is caused by closure of the:✓ Semilunar (aortic and pulmonary) valves
Q35. If the SA node fails, the heart can still beat because the ____ can act as a pacemaker:✓ AV node
Q36. The pacemaker potential (spontaneous depolarisation) of the SA node is due partly to a current called the:✓ Funny (If) current