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

The Heart as a Pump Flashcards

1
Q

Where does the heart pump blood to?

A

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

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2
Q

Via what does blood return to the heart?

A

Capacitance vessels

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3
Q

What do resistance vessels do?

A

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

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4
Q

What do the capacitance vessels enable?

A

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

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5
Q

What do the capacitance vessels act as?

A

A storage facility

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6
Q

Why is the storage facility of capacitance vessels important?

A

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

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7
Q

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

A

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

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8
Q

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

A

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

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9
Q

Which of the circulations is high pressure?

A

Systemic

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10
Q

Which of the circulations is low pressure?

A

Pulmonary

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11
Q

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

A

They must be equal over time

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12
Q

What do the atria act as?

A

‘Priming pumps’ for the ventricles

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13
Q

What is meant by the atria acting as priming pumps?

A

They fill with blood so they can fill the ventricles

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14
Q

What does the right side of the heart do?

A

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

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15
Q

What is between the right ventricle and the pulmonary artery?

A

The pulmonary valve

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16
Q

How does blood in the lungs return to the heart?

A

Through the pulmonary vein into the left atrium

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17
Q

What is between the left atrium and left ventricle?

A

The mitral valve (also known as the bicuspid valve)

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18
Q

What does the left ventricle do?

A

Pumps oxygenated blood to the body through the aorta

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19
Q

What is between the left ventricle and the aorta?

A

The aortic valve

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20
Q

How does blood from tissues return to the heart?

A

Through the superior and inferior vena cava into the right atrium

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21
Q

What is between the right atrium and right ventricle?

A

The tricuspid valve

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22
Q

What is the typical pressure in the left atrium?

A

8-10mmHg

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23
Q

What is the typical pressure in the left ventricle?

A

120mmHg systole / 10mmHg diastole

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24
Q

What is the typical pressure in the aorta?

A

120mmHg systole / 80mmHg diastole

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25
Q

What is the typical pressure in the right atrium?

A

1-4mmHg

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26
Q

What is the typical pressure in the right ventricle?

A

25mmHg systole / 4mmHg diastole

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27
Q

What is the typical pressure in the pulmonary artery?

A

25mmHg systole / 10mmHg diastole

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28
Q

What is systole?

A

Contraction and ejection of the blood from the ventricles

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29
Q

What is diastole?

A

Relaxation and filling of the ventricles

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30
Q

How much does each ventricle pump per beat?

A

~70ml blood

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31
Q

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

A

The stroke volume

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32
Q

What type of muscle is heart muscle?

A

A specialised form of cardiac muscle

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33
Q

Where does ventricular contraction start from?

A

The apex of the heart

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34
Q

Describe the connections of cells in the cardiac muscle?

A

Cells are discrete, but interconnected electrically

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35
Q

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

A

Skeletal muscle has fused cells

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36
Q

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

A

Smooth muscle has individual cells

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37
Q

Why are the cardiac muscles connected?

A

So electrical signals can pass freely through the cells

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38
Q

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

A

Because it allows the heart to beat in sync

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39
Q

What do the cardiac myocytes contract in response to?

A

An action potential in the membrane

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40
Q

What does an action potential in cardiac myocytes cause?

A

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

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41
Q

How long is the cardiac action potential?

A

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

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42
Q

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

A

Relatively long in terms of electrophysiology

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43
Q

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

A

So the contraction of the heart lasts long enough

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44
Q

What are action potential triggered by?

A

A spread of excitation from cell to cell

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45
Q

What determines the pathway of blood through the heart?

A

The 4 valves

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46
Q

What are the 4 valves in the heart?

A

Tricuspid valve
Mitral valve
Pulmonary valve
Aortic valve

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47
Q

What determines the opening and closing of heart valves?

A

The differential pressure on each side

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48
Q

What do valves have?

A

Cusps

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49
Q

What is the purpose of cusps?

A

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

50
Q

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

A

Papillary muscles via chordae tendinae

51
Q

What is the purpose of the papillary muscle connections?

A

It prevents the inversion of valves on systole

52
Q

Where are the pacemaker cells?

A

In the sinoatrial nodes

53
Q

What do the pacemaker cells do?

A

Generate an action potential

54
Q

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

A

The activity spreads over the atria in atrial systole

55
Q

What happens when the signal reaches the atrioventricular node?

A

It is delayed for about 120ms

56
Q

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

A

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

57
Q

What happens in terms of excitation form the AV node?

A

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

58
Q

In what manner does excitation spread through the ventricular myocardium?

A

From inner (endocardial) to outer (epicardial) surface

59
Q

In what manner does the ventricle contract?

A

From the apex up

60
Q

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

A

It forces blood through the outflow valves

61
Q

What are the phases of the cardiac cycle?

A
  1. Atrial contraction
  2. Isovolumetric contraction
  3. Rapid ejection
  4. Reduced ejection
  5. Isovolumetric relaxation
  6. Rapid filling
  7. Reduced filling
62
Q

What do Wiggers diagrams show?

A

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

63
Q

What do Wiggers diagrams typically start at?

A

Atrial contraction

64
Q

How are Wiggers diagrams usually plotted?

A

For the left side of the heart

65
Q

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

A

Very similar, but at lower pressures

66
Q

What is meant by the cardiac cycle?

A

One pump of the heart

67
Q

What does the cardiac cycle consist of?

A

One cycle of systole and diastole

68
Q

What is phase 1 of the cardiac cycle?

A

Atrial contraction

69
Q

What happens to atrial pressure in phase 1?

A

It rises due to atrial systole

70
Q

What is the rise in atrial pressure called?

A

The A wave

71
Q

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

A

To 80% capacity

72
Q

What does atrial contraction provide?

A

The final bit of filling of the ventricles

73
Q

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

A

Age and exercise

74
Q

What happens as the atria contract?

A

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

75
Q

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

A

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

76
Q

What does the P wave in the ECG signify?

A

The onset of atrial depolarisation

77
Q

What state are the valves in during phase 1?

A

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

78
Q

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

A

They are maximal

79
Q

What is maximal ventricular volume termed?

A

End diastolic volume (EDV)

80
Q

Typically, what is EDV?

A

About 120ml

81
Q

What is phase 2 of the cardiac cycle?

A

Isovolumetric contraction

82
Q

What happens in isovolumetric contraction?

A

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
Q

What does the mitral valve closure cause?

A

A C wave in the atrial pressure curve

84
Q

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

A

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

85
Q

Why is this stage termed isovolumetric contraction?

A

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

86
Q

What does the QRS complex in the ECG signify?

A

The onset of ventricular depolarisation, and therefore contraction

87
Q

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

A

The first heart sound

88
Q

What is the first heart sound termed?

A

S1

89
Q

How can valve closures be heard?

A

Using a stethoscope

90
Q

What sound does S1 make?

A

Lub

91
Q

What is phase 3 of the cardiac cycle?

A

Rapid ejection

92
Q

When does ejection begin?

A

When intraventricular pressure exceeds the pressure within the aorta

93
Q

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

A

Because it causes the aortic value to open

94
Q

What does ejection cause?

A

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

95
Q

What happens to atrial pressure during phase 3?

A

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

96
Q

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

A

The X descent

97
Q

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

A

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

98
Q

Why does blood flow into the atria during phase 3?

A

To fill them with blood for the next cycle

99
Q

What is phase 4 of the cardiac cycle?

A

Reduced ejection

100
Q

What happens in reduced ejection?

A

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

101
Q

What is ventricular repolarisation depicted by?

A

The T wave of the ECG

102
Q

What happens to atrial pressure in phase 4?

A

It gradually rises due to the venous return from the lungs

103
Q

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

A

The V wave

104
Q

What is phase 5 of the cardiac cycle?

A

Isovolumetric relaxation

105
Q

What causes isovolumetric relaxation?

A

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
Q

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

A

A dicrotic notch in the aortic pressure curve

107
Q

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

A

Due to elastic reverberation

108
Q

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

A

The second heart sound

109
Q

What is the second heart sound?

A

Dub

110
Q

Why does volume remain constant in isovolumetric relaxation?

A

All the valves are closed

111
Q

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

A

End systolic volume

112
Q

What does stroke volume equal?

A

EDV-ESV

113
Q

What is phase 6 of the cardiac cycle?

A

Rapid filling

114
Q

When does rapid ventricular filling begin?

A

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

115
Q

What does the opening of the mitral valve cause?

A

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

116
Q

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

A

Y-descent

117
Q

What sound does the rapid filling make?

A

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

118
Q

What does the presence of the third heart sound indicate?

A

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

119
Q

What is phase 7 of the cardiac cycle?

A

Reduced filling

120
Q

What happens as the ventricle reaches its inherent relaxed volume?

A

The rate of filling slows down (diastasis)

121
Q

What is reduced filling driven by?

A

Venous pressure

122
Q

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

A

~90%

ESA 2- Cardiovascular System (18 decks)

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