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BRS CARDIO & RESPIRATORY > The Cardiac Cycle > Flashcards

The Cardiac Cycle Flashcards

1
Q

What is cardiac systole?

A

Contraction of the heart

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2
Q

What is cardiac diastole?

A

Relaxation of the heart

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3
Q

How long does diastole last?

A

2/3rds of each beat

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4
Q

How long does systole last?

A

1/3 of each beat

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5
Q

How many stages is diastole split into?

A

4

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6
Q

How many stages is systole split into?

A

3

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7
Q

How many distinct stages of the cardiac cycle are there?

A

7

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8
Q

What are the names of the 7 distinct stages of the cardiac cycle?

A

Atrial Systole
Isovolumetric contraction
Rapid ejection
Reduced ejection
Isovolumetric relaxation
Rapid passive filling
Reduced passive filling

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9
Q

What happens during ventricular relaxation?

A

The ventricles fill with blood

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10
Q

What happens during ventricular contraction?

A

The ventricles generate pressure and then eject the blood into the arteries

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11
Q

What is the end diastolic volume?

A

The volume of blood in the ventricles just before systole

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12
Q

What is the end systolic volume?

A

The volume of blood that remains in the ventricles after systole has occurred

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13
Q

What is the stroke volume in relation to EDV and ESV?

A

The stroke volume is the EDV - ESV

This is because the stroke volume is the amount of blood which is ejected from the ventricles with each contraction of the heart

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14
Q

What are the common figures for EDV, ESV and SV?

A

EDV = 120 ml
ESV = 50 ml
Therefore stroke volume = 70ml

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15
Q

What is the ejection fraction?

A

The (SV / EDV ) x 100

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16
Q

What is the normal range for the ejection fraction?

A

50-70%

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17
Q

What happens to the ejection fraction during heart failure?

A

The ejection fraction decreases to about 30%

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18
Q

How is the ejection fraction used clinically?

A

It is used to assess the degree of heart failure a patient may have

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19
Q

Where is the tricuspid valve located?

A

Between the right atrium and right ventricle

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20
Q

Where is the bicuspid or mitral valve located?

A

Between the left atrium and the left ventricle

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21
Q

Where is the pulmonary valve located?

A

Between the right ventricle and the pulmonary artery

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22
Q

Where is the aortic valve located?

A

Between the left ventricle and the aorta

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23
Q

What is atrial systole?

A

Contraction of the atria to top up the volume of blood in the ventricle

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24
Q

What wave on the ECG correlates with atrial systole?

A

P wave

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25
Q

What might be heard during atrial systole?

A

An abnormal heart sound due to valve incompetence of the atrioventricular valves (tricuspid)

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26
Q

In what conditions might a sound be heard during atrial systole?

A

Congestive heart failure, pulmonary embolism or tricuspid incompetence

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27
Q

What does the QRS complex symbolize?

A

Depolarization of the ventricular muscle

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28
Q

What is isovolumetric contraction?

A

When there is contraction of the ventricles to build pressure (isometric contraction), but no change in the volume of blood in the ventricles

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29
Q

What heart sound is heard during isovolumetric contraction?

A

Lub

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30
Q

What is the status of the AV and SL valves during isovolumetric contraction?

A

They are all closed

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31
Q

What causes the first heart sound, “lub”?

A

The closure of the AV valves

32
Q

What marks the start of the rapid ejection phase?

A

The opening of the SL valves

33
Q

What happens during the rapid ejection phase?

A

The ventricular pressure is larger than the aortic pressure, (overcomes the afterload) meaning the blood pushes against the aortic valve and pushes out the ventricle

34
Q

What type of muscle contraction occurs during rapid ejection stage of cardiac cycle?

A

Isotonic contraction

35
Q

What happens to the pressure in the ventricles during reduced ejection stage?

A

The ventricular pressure starts to fall

36
Q

What phase marks the end of systole?

A

Reduced ejection

37
Q

What causes the SL valves to start to close in the reduced ejection phase?

A

The reduced pressure gradient

38
Q

What happens to the calcium during the reduced ejection phase?

A

The calcium is being pumped back into the extracellular space, out the cell, causing the calcium levels to fall back to diastolic calcium levels

39
Q

What part of the ECG represents reduced ejection?

A

T wave

40
Q

What happens when the ventricular pressure is less than aortic pressure?

A

The semilunar valves close to prevent the back flow of blood

41
Q

What happens to the ventricular pressure during isovolumetric relaxation?

A

Large decrease

42
Q

What happens to atrial pressure during isovolumetric relaxation?

A

It continues to rise

43
Q

What causes the dichrotic notch seen on the ECG?

A

Rebound pressure against the aortic valve as distended aortic wall relaxes

44
Q

What causes the second heart sound “dub”?

A

The complete closure of the SL valves

45
Q

What happens during the rapid passive filling phase?

A

The AV valves open and so blood from the atria flows into the ventricles, resulting in a large increase in ventricular volume

46
Q

What might a sound heard during rapid passive filling signify?

A

Turbulent ventricular filling, hypertension or mitral incompetance

47
Q

What is the abnormal S3 sound called?

A

Ventricular gallop

48
Q

What is diastasis?

A

Reduced passive filling phase

49
Q

What happens to ventricular volume during reduced passive filling?

A

The ventricles fill slowly with blood, without the contraction of the atria

50
Q

What is the relationship between the pressure change patterns in the right and the left of the heart?

A

They are identical

51
Q

Which side of the heart has quantitively a higher pressure?

A

The left side has a higher pressure

52
Q

Which side of the heart pumps more blood?

A

They pump the same amount

53
Q

What is the average blood pressure in the systemic circuit?

A

Let side of the heart pumps blood to body - 120/80

54
Q

What is the average blood pressure in the pulmonary circuit?

A

Right side of the body pumps deoxygenated blood to the lungs - 25/5 mmHg

55
Q

What is the pressure of the atria relative to the ventricle?

A

The pressure in the right atrium is significantly lower than the right ventricle

56
Q

How are pressure volume loops used clinically?

A

They are used to assess contractility

57
Q

What do the A,B,C AND D points on a pressure volume loop relate to?

A

A = End Diastolic volume, preload
B = when the ventricle encounters the Afterload
C = End systolic volume
D = ventricular pressure has dropped as blood is pumped out the heart

58
Q

What happens to the stroke volume if you increase the preload?

A

Increasing the stretch, means that the length of the muscle fibers increase, which increases the force (due to more Ca2+ sensitivity), so more blood can be expelled with each beat of the heart

59
Q

What happens to stroke volume when you increase the afterload?

A

If you increase the pressure which the ventricles face, the fibers cannot shorten as much as there is a heavy weight acting against them, so the stroke volume decreases

60
Q

If you increase the afterload, what happens to the amount of shortening the muscle fibres undergo?

A

They shorten less

61
Q

What does the End Systolic PV line show?

A

The maximal pressure that can be developed by the ventricle at any given volume

62
Q

What happens to the pressure volume loop when you increase preload?

A

Points A and B shift to the right, which increases the stroke volume due to an increase in venous return

63
Q

Why does an increase in preload also increase the SV?

A

More stretch on the muscle due to more venous return changes their sensitivity to Ca2+ so more cross bridges can form which increases the force of contraction, hence SV increases as more blood can then be expelled per beat

64
Q

Describe what happens to the pressure volume loop when there is an increase in afterload?

A

Points C and D shift to the right
Point C also rises

65
Q

How do you calculate cardiac output?

A

Cardiac output = stroke volume x heart rate

66
Q

What three factors does stroke volume depend on?

A

Preload, afterload and contractility

67
Q

What is contractility?

A

The contractile capability of the heart

68
Q

What happens to the ESPVR line when contractility is increased?

A

It gets steeper = more Ca2+ is delivered to the myofilaments so for a smaller stretch there is more force produced

69
Q

What happens to the ESPVR line when there is a decrease in contractility?

A

Less Ca2+ to myofilaments, therefore less force is produced as fewer cross bridges are formed

70
Q

What increases the contractility?

A

Sympathetic stimulation

71
Q

What factors increase venous return?

A

Muscle and Respiratory pump

72
Q

What happens when the myocytes are sympathetically activated?

A

The ventricular contractility increases which decreases the end systolic volume so stroke volume increases

73
Q

What happens to atrial pressure during exercise? And what affect does this have on the afterload?

A

It increases, and increases afterload as well

74
Q

What happens if the HR increases to very high rates?

A

The diastolic filling time can be reduced, which increases EDV

75
Q

What is the end systolic volume?

A

The volume of blood that remains in the heart even after the ventricle has contracted fully

76
Q

What are the two mechanisms by which the SA node rate is increased sympathetically?

A
  1. Hormonal - adrenaline
  2. Neural - noradrenaline from nerves
77
Q

What affect does hardening of the aortic valve have on the afterload?

A

Increases the afterload

BRS CARDIO & RESPIRATORY (26 decks)

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