The Heart as a Pump Flashcards Preview

ESA 2- Cardiovascular System > The Heart as a Pump > Flashcards

Flashcards in The Heart as a Pump Deck (122):
1

Where does the heart pump blood to?

Exchange vessels in the lungs, and then through resistance vessels to the exchange vessels in the tissue

2

Via what does blood return to the heart?

Capacitance vessels

3

What do resistance vessels do?

Restrict blood flow, to drive supply to the hard to perfuse areas of the body

4

What do the capacitance vessels enable?

The system to vary the amount of blood pumped around the body

5

What do the capacitance vessels act as?

A storage facility

6

Why is the storage facility of capacitance vessels important?

Means that different amounts of blood can be in the circulation, so supply can change to meet demand

7

What would happen if the circulatory system was just a simple system with pumps and pipes?

It wouldn’t work very well as the blood would go to the easiest places to perfuse

8

How do the resistance vessels prevent blood just going to the places that are easiest to perfuse?

They stop blood going to some areas, so the blood has to go elsewhere

9

Which of the circulations is high pressure?

Systemic

10

Which of the circulations is low pressure?

Pulmonary

11

What must be true of the outputs of the left and right sides?

They must be equal over time

12

What do the atria act as?

‘Priming pumps’ for the ventricles

13

What is meant by the atria acting as priming pumps?

They fill with blood so they can fill the ventricles

14

What does the right side of the heart do?

Pumps deoxygenated blood from the right ventricle through the pulmonary artery to the lungs for oxygenation

15

What is between the right ventricle and the pulmonary artery?

The pulmonary valve

16

How does blood in the lungs return to the heart?

Through the pulmonary vein into the left atrium

17

What is between the left atrium and left ventricle?

The mitral valve (also known as the bicuspid valve)

18

What does the left ventricle do?

Pumps oxygenated blood to the body through the aorta

19

What is between the left ventricle and the aorta?

The aortic valve

20

How does blood from tissues return to the heart?

Through the superior and inferior vena cava into the right atrium

21

What is between the right atrium and right ventricle?

The tricuspid valve

22

What is the typical pressure in the left atrium?

8-10mmHg

23

What is the typical pressure in the left ventricle?

120mmHg systole / 10mmHg diastole

24

What is the typical pressure in the aorta?

120mmHg systole / 80mmHg diastole

25

What is the typical pressure in the right atrium?

1-4mmHg

26

What is the typical pressure in the right ventricle?

25mmHg systole / 4mmHg diastole

27

What is the typical pressure in the pulmonary artery?

25mmHg systole / 10mmHg diastole

28

What is systole?

Contraction and ejection of the blood from the ventricles

29

What is diastole?

Relaxation and filling of the ventricles

30

How much does each ventricle pump per beat?

~70ml blood

31

What is how much each ventricle pumps per beat known as?

The stroke volume

32

What type of muscle is heart muscle?

A specialised form of cardiac muscle

33

Where does ventricular contraction start from?

The apex of the heart

34

Describe the connections of cells in the cardiac muscle?

Cells are discrete, but interconnected electrically

35

How does the connections of cardiac muscle differ from skeletal muscle?

Skeletal muscle has fused cells

36

How doe the connections of cardiac muscle differ from smooth muscle?

Smooth muscle has individual cells

37

Why are the cardiac muscles connected?

So electrical signals can pass freely through the cells

38

Why is the ability for electrical signals to pass through cells important?

Because it allows the heart to beat in sync

39

What do the cardiac myocytes contract in response to?

An action potential in the membrane

40

What does an action potential in cardiac myocytes cause?

A rise in intracellular calcium, the key driver of muscle contraction

41

How long is the cardiac action potential?

Lasts for the duration of a single contraction of the heart, which is about 280ms

42

How does the duration of the cardiac output compare to usual?

Relatively long in terms of electrophysiology

43

What is the purpose of the long duration of the cardiac action potential?

So the contraction of the heart lasts long enough

44

What are action potential triggered by?

A spread of excitation from cell to cell

45

What determines the pathway of blood through the heart?

The 4 valves

46

What are the 4 valves in the heart?

Tricuspid valve
Mitral valve 
Pulmonary valve 
Aortic valve

47

What determines the opening and closing of heart valves?

The differential pressure on each side

48

What do valves have?

Cusps

49

What is the purpose of cusps?

They are pushed open to allow blood flow, and close together to seal and prevent backflow

50

What do cusps of the mitral and tricuspid valves attach to?

Papillary muscles via chordae tendinae

51

What is the purpose of the papillary muscle connections?

It prevents the inversion of valves on systole

52

Where are the pacemaker cells?

In the sinoatrial nodes

53

What do the pacemaker cells do?

Generate an action potential

54

What happens once the pacemaker cells have generated an action potential?

The activity spreads over the atria in atrial systole

55

What happens when the signal reaches the atrioventricular node?

It is delayed for about 120ms

56

What is the purpose of the delay facilitated by the atrioventricular node?

So the ventricles don’t contract at the same time as the atria

57

What happens in terms of excitation form the AV node?

Excitation spreads down the Purkinje fibres in the septum between the ventricles. Then, it spreads through the ventricular myocardium

58

In what manner does excitation spread through the ventricular myocardium?

From inner (endocardial) to outer (epicardial) surface

59

In what manner does the ventricle contract?

From the apex up

60

What is the result of the ventricle contracting from the apex out?

It forces blood through the outflow valves

61

What are the phases of the cardiac cycle?

1. Atrial contraction


2. Isovolumetric contraction


3. Rapid ejection


4. Reduced ejection


5. Isovolumetric relaxation


6. Rapid filling


7. Reduced filling

62

What do Wiggers diagrams show?

The changes that occur in pressure, and the simultaneous changes in volume

63

What do Wiggers diagrams typically start at?

Atrial contraction

64

How are Wiggers diagrams usually plotted?

For the left side of the heart

65

How would a Wiggers diagram of the right side of the heart appear?

Very similar, but at lower pressures

66

What is meant by the cardiac cycle?

One pump of the heart

67

What does the cardiac cycle consist of?

One cycle of systole and diastole

68

What is phase 1 of the cardiac cycle?

Atrial contraction

69

What happens to atrial pressure in phase 1?

It rises due to atrial systole

70

What is the rise in atrial pressure called?

The A wave

71

How full are the ventricles from the previous contraction in phase 1?

To 80% capacity

72

What does atrial contraction provide?

The final bit of filling of the ventricles

73

What does the amount the atria fill the ventricles vary with?

Age and exercise

74

What happens as the atria contract?

They push blood from the atria to the ventricles, giving a small rise in pressure in the ventricles

75

Why is the pressure rise in the ventricles during phase 1 only small?

Because the atria are only providing the final 10% of ventricular filling

76

What does the P wave in the ECG signify?

The onset of atrial depolarisation

77

What state are the valves in during phase 1?

The mitral and tricuspid valves are open, and the aortic and pulmonary valves are closed

78

What has happened to ventricular volumes at the end of phase 1?

They are maximal

79

What is maximal ventricular volume termed?

End diastolic volume (EDV)

80

Typically, what is EDV?

About 120ml

81

What is phase 2 of the cardiac cycle?

Isovolumetric contraction

82

What happens in isovolumetric contraction?

There is a rapid rise in ventricular pressure as the ventricles contract. This means that intraventricular pressure exceeds atrial pressure, so the mitral valve closes

83

What does the mitral valve closure cause?

A C wave in the atrial pressure curve

84

Why does the mitral valve closure cause a C wave in the pressure curve?

As the valve is being pushed back into the atria, there is a transient increase in pressure at the C wave

85

Why is this stage termed isovolumetric contraction?

Because there is no change in ventricular volume, as all the valves are closed so there is nowhere for blood to go

86

What does the QRS complex in the ECG signify?

The onset of ventricular depolarisation, and therefore contraction

87

What does closure of the mitral and tricuspid valve result in?

The first heart sound

88

What is the first heart sound termed?

S1

89

How can valve closures be heard?

Using a stethoscope

90

What sound does S1 make?

Lub

91

What is phase 3 of the cardiac cycle?

Rapid ejection

92

When does ejection begin?

When intraventricular pressure exceeds the pressure within the aorta

93

Why does ejection begin when intraventricular pressure exceeds the pressure within the aorta?

Because it causes the aortic value to open

94

What does ejection cause?

A rapid decrease in the volume of blood in the ventricles, as it rapidly moves into the aorta

95

What happens to atrial pressure during phase 3?

It initially decreases as the atrial base is pulled downwards as the ventricle contracts

96

What is the decrease in atrial pressure during phase 3 called?

The X descent

97

What happens to volume of blood in the atria during phase 3?

At this point, blood is continuing to flow into the atria from their respective venous inputs

98

Why does blood flow into the atria during phase 3?

To fill them with blood for the next cycle

99

What is phase 4 of the cardiac cycle?

Reduced ejection

100

What happens in reduced ejection?

Repolarisation of the ventricle leads to a decline in tension, the rate of ejection begins to fall

101

What is ventricular repolarisation depicted by?

The T wave of the ECG

102

What happens to atrial pressure in phase 4?

It gradually rises due to the venous return from the lungs

103

What is the rise in atrial pressure in phase 4 called?

The V wave

104

What is phase 5 of the cardiac cycle?

Isovolumetric relaxation

105

What causes isovolumetric relaxation?

When the intraventricular pressure falls below aortic pressure due to a decline in tension, there is a brief backflow of blood which causes the aortic valve to close.

106

What does the closure of the aortic valve cause in phase 5?

A dicrotic notch in the aortic pressure curve

107

Why does the closure of the aortic valve cause a dicrotic notch in the aortic pressure curve?

Due to elastic reverberation

108

What does closure of the aortic and pulmonary valve result in?

The second heart sound

109

What is the second heart sound?

Dub

110

Why does volume remain constant in isovolumetric relaxation?

All the valves are closed

111

What is the volume in the left ventricles after phase 5 termed?

End systolic volume

112

What does stroke volume equal?

EDV-ESV

113

What is phase 6 of the cardiac cycle?

Rapid filling

114

When does rapid ventricular filling begin?

When the intraventricular pressure falls below the atrial pressure, causing the mitral valve to open

115

What does the opening of the mitral valve cause?

Passive blood flow into the ventricles, and hence a fall in atrial pressure

116

What is the fall in atrial pressure in rapid filling called?

Y-descent

117

What sound does the rapid filling make?

It is normally silent, however a third heart sound is normally present

118

What does the presence of the third heart sound indicate?

It is normal in children, but can be a sign of pathology in adults

119

What is phase 7 of the cardiac cycle?

Reduced filling

120

What happens as the ventricle reaches its inherent relaxed volume?

The rate of filling slows down (diastasis)

121

What is reduced filling driven by?

Venous pressure

122

How full are the ventricles at rest by the end of phase 7?

~90%