1. Starter - review Using these key words write 3 sentences about the human circulatory system. What are the parts of the circulatory system? What is its function (job)? How is it designed to do this function ? Words: Closed, transport, pump, blood, double, pressure, oxygenated, deoxygenated, blood vessels

2. Lesson Aims How is the structure of the heart related to its function? 5.6 litres How much blood does the human body contain?

3. The Heart Between the two lungs Enclosed by the PERICARDIUM Pericardial fluid is secreted between them to aid movement The pericardium protects the heart from over expansion Where is it?

4. The walls of the heart are made of cardiac muscle (MYOCARDIUM) Only found in heart Never tires but can’t tolerate lack of O 2. Hold your hand in front of you and make a fist. Squeeze and relax. How long can you do this for?

5. Activity Drag the labels to the right place to complete the diagram and the key

6. (bicuspid valve) Septum Pericardial membranes Semi-lunar valves Internal Features

7. Internal Structure Task: Add labels to the diagram

8. Watch this Video Blood flow through the heart nearly 12,000 miles How far does your blood travel in one day?

9. Blood flow through the heart Blood comes into the heart from the body It then has to pass to the lungs to collect oxygen This is called a double circulatory system After it returns to the heart it leave again to be transported to the body. Task: Draw a flow diagram to show the flow of blood through the heart. You should start and finish with the body.

10. Atrium- receives blood from veins Ventricle- pumps blood into arteries Right Left Deoxygenated blood atrium Tricuspid valve Right ventricle Pulmonary artery lungs Pulmonary vein Oxygenated blood atrium Bicuspid valve Left ventricle body aorta Vena cava Body

11. External Features

12. External Structure Task: Add labels to your diagram

13. Heart Dissection around 35 million times How many times does the heart beat in a lifetime?

14. Your sheep’s heart What external features can you identify? A C B D F E a million barrels of blood How much blood does the heart pump in a lifetime?

15. External Features FRONTBACK Apex

16. Intact Heart… This shows the heart from the front, with the portion on the right of the picture being the left side of the heart and vice versa. The aorta is clearly visible at the top, with an atrium on either side, while the ventricles are in the bottom left.

17. The first incision… … is along the right ventricle. The right ventricle can be identified by squeezing the heart, since the myocardium on the right side is much less rigid than that of the left ventricle. This allows us to see the tricuspid valve and the right ventricular outflow tract which includes the pulmonary valve.

18. Longitudinal Cut… The right ventricle has been cut open from the bottom towards the top. In this picture, the myocardium is being held back. My finger is stuck underneath one leaflet of the tricuspid valve, which leads to the pulmonary valve.

19. The Tricuspid Valve up close… The tricuspid valve allows blood to flow from the right atrium into the right ventricle.

20. Pulmonary Valve… When the heart is contracting, the pulmonary valve is open because the blood pushes the cusps out of the way. After contracting, the ventricles begin to relax and the pulmonary valve closes and prevents back- flow (called regurgitation) of blood into the ventricle.

21. The Left Ventricle… This longitudinal incision extends from the bottom to the top of the left ventricle, then continues up into the atrium to allow us to view the entire left heart.

22. The Mitral (bicuspid) valve… The mitral valve prevents blood from flowing back into the left atrium The mitral valve is positioned between the atrium (at top) and ventricle (at bottom).

23. Left Ventricular Outflow… Blood flows into the ventricles by passing through the mitral valve, but can you see where it flows out? This is a bit of a trick question because the outflow tract is hidden behind the mitral valves

24. What to do next! Answer the questions on the worksheet Match the keywords and their definitions

25. 1. Why are pig or sheep hearts used to study the anatomy of the human heart? 2. How can you tell which side of the heart is the ventral surface? 3. How many chambers are found in the mammalian heart? What other group of organisms would have this same number of chambers? 4. What is the advantage in having this number of chambers compared to organisms with a fewer number of chambers? 5. Which chambers are the pumping chambers of the heart? 6. Which chambers are the receiving chambers of the heart? 7. How do the walls of the atria compare with the walls of the ventricles and why are they different? 8. What is the purpose of heart valves? 9. Name & compare the heart valves found between the upper & lower chambers of the right and left sides of the heart. 10. Vessels that carry blood away from the heart are called __________, while __________ carry blood toward the heart. 11. Which artery is the largest and why? 12. What is the purpose of the coronary artery and what results if there is blockage in this vessel? 13. Use the diagram of the heart below to trace blood flow through the heart: Questions to answer after the dissection

26. Oxygenated Relating to the lungs Deoxygenated The valve which prevents backflow from the pulmonary artery to the right ventricle Pulmonary vein Separates the two sides of the heart, keeping oxygenated and deoxygenated blood apart. Pulmonary artery Blood vessels on the surface of the heart which supply the heart itself with blood. Aorta Blood without oxygen (usually coloured blue on a diagram) Vena cava The valve which prevents backflow from the right ventricle to the right atrium Ventricle The major blood vessel which carries oxygenated blood from the heart to the body. Atrium Relating to the body Mitral valve One of the bottom two chambers of the heart Tricuspid valve Blood with oxygen (usually coloured red on a diagram) Pulmonary valve One of the top two chambers of the heart Aortic valve Blood vessel which returns with oxygenated blood from the lungs to the left atrium Septum The muscle of the heart, cardiac muscle which never fatigues (gets tired) Myocardium Blood vessel which leaves the right ventricle transporting deoxygenated blood to the lungs Pulmonary Valve which prevents backflow from the aorta to the left ventricle Systemic The valve which prevents backflow from the left ventricle to the left atrium Coronary artery The major blood vessel which returns deoxygenated blood to the heart from the body

27. Activity Drag the labels to the correct numbered boxes on the diagram of the blood system

28. The Circulatory System

29. Valves prevent backflow When pressure in ventricles exceeds that in the atrium the bicuspid/tricuspid valves shut This makes the first noise we hear with a stethoscope. Tendinous chords attached to Papillary Muscles prevent valves turning inside out. Semi-lunar valves prevent backflow in the pulmonary artery and dorsal aorta. Closure of these makes the second noise of the heart beat. (hence lub-dub)

30. The heart requires a lot of oxygen and nutrients Some oxygenated blood leaving the left ventricle goes directly to the heart through the coronary Arteries. These branch many times to supply oxygen and nutrients throughout the cardiac muscle. When these get blocked a heart attack is likely and by-pass surgery required.

31. Task: Label the diagram of the circulatory system Follow the red blood cell through the circulatory system Follow the red blood cell through the circulatory system

32. The Cardiac Cycle Cardiac muscle contracts without nervous or hormonal stimulation these are MYOGENIC contractions. The muscle cells work together to produce the heartbeat (cardiac cycle) Heart beat animation

34. The cycle starts at the Sinoatrial node (SA node) A small piece of tissue with a inherent rhythm of contraction. The rhythm can be slowed or sped by nervous impulses and hormones. The SA node is also known as the pacemaker The SA node generates waves of electrical impulses called cardiac impulses.

35. The electrical impulses pass over the atria until they hit the Atrioventricular septum This is non-conductive with only one gap in it called the Atrioventricular Node (AV node) This is the only route for cardiac impulse transmission. This is the second pacemaker and can take over if the SA node malfunctions Conducting sytem of the heart animation

36. Cardiac Cycle Cardiac Cycle animation

37. Systole (contraction) a)Atrial systole Atria contract Semi-lunar valves closed Blood forced from the atria into the ventricle b)Ventricular systole Ventricle contracts Blood is forced into arteries Bicuspid and tricuspid valves closed

38. Systole (contraction) Cardiac impulse relayed from AV node over the ventricles through the Bundle of His (atrioventricular bundle) Bundle branches into Purkinje (Purkyne) Fibres The cardiac impulse passing through the fibres causes a wave of contraction. It starts at the apex of the heart and rapidly passes over the ventricles (ventricular systole) Regions close to the AV node have thin fibres therefore slow the impulse so all ventricle contracts at once.

39. Diastole (relaxation) Heart relaxes and fills with blood from the veins. Semi-lunar valves closed to blood entering through arteries. Cardiac Cycle Tutorial Task: Order the diagrams of the cardiac cycle and annotate.

40. Pressure Changes

41. You need to be able to explain the pressure changes in the heart in. terms of what is happening inside the heart You also need to be able to identify where the valves open and close and explain why in terms of pressure Task: Label this diagram of pressure changes in the heart. What is happening at A, B, C and D?

42. Answer these questions: Explain the difference in pressure between the atria and the ventricles. What causes the valves to open and close?

43. Pressure changes in the heart Atrium has lower max pressure as only pumps blood into the ventricle; ventricle pumps to the whole body. Closure of the valves is a passive process; it depends on the relative pressures on either side of the valve. The Atrioventricular valves close when the pressure in the ventricles is higher than in the atrium. They open when the pressure is higher in the atrium than the ventricle.

44. Cardiac Cycle Overview

46. An Electrocardiogram - ECG R P QS T Cardiac muscle contracts as a result of electrical stimulation, this is detected with recording electrodes. Electrical signals are shown on a cathode ray oscilloscope or a chart recorder; this is an ECG. A single cardiac cycle: P = atrial systole; QRS = wave of ventricular systole; T = ventricular diastole ECG changes in a diseased heart are used by doctors for diagnosis heart rate calculated from interval between P waves P

47. Interpreting an ECG Trace

48. Electrocardiogram animation

49. Cardiac output Average resting for a man is 75cm 3 (stroke) and 70 beats per minute (rate) When exercising both stroke and rate increase The fitter a person is the lower the resting rate and higher stroke volume. Cardiac Output = Stroke Volume X Heart rate ( Volume of blood leaving left ventricle with each beat) (beats per minute)

50. As the heart beats, it releases regular surges (increased volumes) of blood. As these pass along the arteries, the vessel must stretch to allow it to pass. This stretching pushes on the skin, which we sense as a pulse. Skin surface Blood flow Heart rate is measured by the pulse

51. Although the heart has its own rhythm it is also regulated by the nervous and hormonal systems. Sensory receptors in the walls of heart and blood vessels are sensitive to changes in blood pressure These send impulses to the CARDIORESPIRATORY CENTRE in the medulla oblongata A vagus nerve branch leads to the SA node. The vagus nerve is part of the Parasympathetic Nervous System and so is an inhibitory nerve, impulses slow the heart rate. Control of the heart beat

52. Branches of a sympathetic nerve also lead to the heart, these impulses will speed up the heart rate. When excited or in danger the sympathetic nervous system also stimulates the release of Adrenaline from the adrenal glands. Adrenaline increase the strength (stroke) and speed (rate) of the heart. The cardiac output is therefore modified by the parasympathetic and sympathetic nervous systems.

53. The cardiac output also varies with the Venous Return (volume of blood returning to heart) If venous return is high, walls of atrium are stretched, which is detected by stretch receptors. The effect of this is that the heart beats faster; this is called the Bainbridge reflex. High venous return also stretches the ventricle wall, this results in the ventricle contracting stronger, giving a greater stroke volume; this is called the Frank-Starling Effect.