Qu.1. How long is each heart beat?

1. Qu.1. How long is each heart beat? 1 cardiac cycle lasts 0.75secs, so heart rate = 60/0.75 = 80 beats/min

2. 1 The AV valve closes at 1 because the pressure of blood in the ventricle is greater than in the atrium. Qu.2 Explain why the AV valve closes at 1?

3. 2 The semilunar valve opens at 2 because the pressure of blood in the ventricle is greater than in the aorta. Qu.2 Explain why the semilunar valve opens at 2?

4. 3 The semilunar valve closes at 3 because the ventricle is empty so the pressure in the aorta is greater than in the ventricle. Qu.3 Explain why the semilunar valve closes at 3?

5. 4 The AV valve opens at 4 because the ventricle is empty so the pressure in the atrium is greater. Qu.2 Explain why the AV valve opens at 4?

6. LO: To describe how heart action is coordinated

7. Cardiac muscle = myogenic • This means it can iniate its own contractions. • The 4 chambers of the heart need coordination to prevent inefficient contractions.

9. R A L A R V L V

10. R A L A R V L V

11. sino-atrial node (SAN) R A L A R V L V

12. R A L A SAN R V L V

13. R A L A SAN R V L V

14. R A L A SAN R V L V

15. R A L A SAN R V L V

16. R A L A SAN R V L V

17. A wave of depolarisation originating at the SAN spreads across the atria… R A L A SAN R V L V

18. A wave of depolarisation originating at the SAN spreads across the atria… …and causes them to contract… R A L A SAN R V L V

19. R A L A R V L V

20. L A R A R V L V

21. L A R A R V L V

22. this causes the atria to contract… ..forcing blood into the ventricles. SAN L A R A R V L V

23. A wave of depolarisation originating at the SAN spreads across the atria… …and causes them to contract… ..forcing blood into the ventricles. SAN L A R A R V L V

24. The wave of depolarisation is prevented from travelling to the ventricles by an insulating layer of connective tissue R A L A SAN R V L V

25. The wave of depolarisation is prevented from travelling to the ventricles by an insulating layer of connective tissue R A L A SAN R V L V

26. atrio-ventricular node (AVN) R A L A SAN R V L V

27. atrio-ventricular node (AVN) R A L A SAN The only route for transmission to the ventricles is the AVN R V L V

28. AVN SAN R A L A R V L V Bundle of His – made of Purkyne tissue

29. AVN The wave of depolarisation travels down the bundle of His SAN R A L A R V L V Bundle of His – made of Purkyne tissue

30. AVN The wave of depolarisation travels down the bundle of His SAN R A L A R V L V Bundle of His – made of Purkyne tissue

31. AVN The wave of depolarisation travels down the bundle of His SAN R A L A R V L V Bundle of His – made of Purkyne tissue

32. AVN The wave of depolarisation travels down the bundle of His SAN R A L A R V L V Bundle of His – made of Purkyne tissue

33. AVN The wave of depolarisation travels down the bundle of His SAN R A L A R V L V Bundle of His – made of Purkyne tissue

34. AVN When it reaches the apex of the ventricles a wave of depolarisation spreads up across the ventricles… SAN R A L A R V L V Bundle of His – made of Purkyne tissue

35. AVN When it reaches the apex of the ventricles a wave of depolarisation spreads up across the ventricles… SAN R A L A R V L V Bundle of His – made of Purkyne tissue

36. AVN When it reaches the apex of the ventricles a wave of depolarisation spreads up across the ventricles… SAN R A L A R V L V Bundle of His – made of Purkyne tissue

37. AVN When it reaches the apex of the ventricles a wave of depolarisation spreads up across the ventricles… SAN R A L A R V L V Bundle of His – made of Purkyne tissue

38. AVN When it reaches the apex of the ventricles a wave of depolarisation spreads up across the ventricles… SAN R A L A R V L V Bundle of His – made of Purkyne tissue

39. AVN …causing them to contract from the apex. SAN R A L A R V L V Bundle of His – made of Purkyne tissue

40. AVN …causing them to contract from the apex. SAN R A L A R V L V Bundle of His – made of Purkyne tissue

41. AVN …causing them to contract from the apex. SAN R A L A R V L V Bundle of His – made of Purkyne tissue

42. AVN …causing them to contract from the apex. R A SAN L A R V L V Bundle of His – made of Purkyne tissue

43. AVN …causing them to contract from the apex. R A SAN L A R V L V Bundle of His – made of Purkyne tissue

44. Because the SAN initiates the heartbeat by creating electrical stimuli at regular intervals. • Why is the SAN known as the pacemaker? (1 mark) • Why do the ventricles contract from the apex (base) up? (1 mark) So that it ensures the ventricles are fully emptied, by squeezing all the blood upwards towards the major arteries.

45. What is the purpose of the impulses running very quickly down the Bundle of His & Purkyne tissue? (1 mark) • Why do the cardiac muscle need coordination? (2 marks) So that it ensures the ventricles contract from the bottom upwards- so they are fully emptied. Else it would lead to inefficient contractions such as fibrillation. The chambers would be unable to fill properly so the heart would not be able to pump the correct amount at each heart beat.

46. Complete “Control of heart activity” w/s