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CVS > S2L1 - heart as a pump > Flashcards

S2L1 - heart as a pump Flashcards

1
Q

On what side of the heart is the pulmonary circulation?

A

Right side

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2
Q

On what side of the heart is the systemic circulation?

A

Left side

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3
Q

How is the contraction of myocardial cells produced?

A

By a rise in intracellular calcium concentration triggered by an action potential.

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4
Q

How long does the contraction of a myocardial cell last?

A

200-300ms

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5
Q

How are the action potentials required for myocardial contraction generated?

A

Generated spontaneously at regular intervals by specialised pacemaker cells. In a normal heart, the pacemaker is the sink-atrial node in the right atrium.

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6
Q

How does excitation spread through the myocardium?

A

Muscle cells are joined by low electrical resistance connections. The excitation from the sino atrial node spreads across the atria to the atrialventricular node, and continues down the muscular septum between the ventricles to excite ventricular muscle from the endocardial side. The contraction then spreads through the ventricular myocardium and up towards the AV junction.

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7
Q

What is systole?

A

The period in which the myocardium is contracting

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8
Q

What is diastole?

A

The period of relaxations between contraction

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9
Q

When does ventricular filling occur?

A

As the ventricular muscle relaxes, the intra ventricular pressure falls and the atrioventricular valves open as the atrial pressure exceeds the ventricular pressure. The atria are distended by continuing venous return during the preceding systole and therefore empty into the ventricles.

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10
Q

What is the rapid filling phase?

A

Quick filling of the ventricles when the atrio ventricular valves open. Occurs as atria are distended and therefore blood is initially rapidly forced into the ventricles

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11
Q

When does diastole finish?

A

Finishes when the intraventricular pressure matches the intra atrial pressure, and the atrioventricular valves close

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12
Q

What is atrial systole?

A

Contraction of the atria, forcing a little extra amount of blood into the ventricles

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13
Q

What happens when intraventricular pressure exceeds intra-atrial pressure after diastole?

A

Ventricle systole begins. Blood flows the wrong way, producing turbulence which forcibly closes the valves.

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14
Q

When do the outflow valves open?

A

During ventricular systole. When the intra ventricular pressure exceeds that of the diastolic pressure in the arteries.

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15
Q

What causes the first normal heart sound (lub)?

A

As the AV valves close, oscillations are induced in a variety of structures including the column of blood in the arteries.

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16
Q

What causes the second heart sound (dub)?

A

The semi-lunar outflow valves close. Oscillations are induced in other structures including the column of blood in the arteries.

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17
Q

When is a third heart sound often heard?

A

In the early stages of diastole, when the AV valves open

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18
Q

Occasionally a fourth heart sound is heard. What is this associated with?

A

Atrial contraction

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19
Q

What are murmurs?

A

Sound produced by turbulent flow in arteries

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20
Q

When are murmurs normal in healthy people?

A

During exercise

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21
Q

What causes murmurs in a patient at rest?

A

Disturbed flow, such as through a narrowed valve, or backflow through an incompetent valve.

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22
Q

Define cardiac output

A

The volume of blood pumped per minute by the left hand side of the heart

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23
Q

What calculation is used to determine the cardiac output?

A

Stroke volume x heart rate.

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24
Q

Where must blood vessels of the heart lie?

A

In grooves between different chambers of the heart

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25
Q

What three sources does the right atrium receive deoxygenated blood from?

A

The inferior vena cava, the superior vena cava and the coronary sinus.

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26
Q

Where can pectinate fibres be seen?

A

On the inner surface of the right atrium wall.

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27
Q

Where can the fossa ovalis be seen?

A

Seen as a depression between the right and left atria.

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28
Q

Where are the chorded tendinae located?

A

Attach to the flaps of the atrioventricular valves.

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29
Q

Where can the papillary muscles be seen?

A

On the inner wall of the ventricles, pull on the choruses tendinae.

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30
Q

Where can the trabeculae carnaea be seen?

A

On the inner wall of the ventricles.

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31
Q

How does the blood pressure vary between the systemic and pulmonary circulation?

A

Systemic circulation = high pressure

Pulmonary circulation = low pressure

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32
Q

What is the typical pressure of the left ventricle?

A

120 systole/ 10 diastole

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33
Q

What is the typical pressure in the right ventricle?

A

25 systole/ 4 diastole

34
Q

At rest what is the average stroke volume?

A

70ml per beat

35
Q

What sort of muscle is in the heart?

A

Cardiac muscle, a form of Striated muscle

36
Q

How long is a cardiac action potential?

A

Relatively long. 280ms. The time it takes for a single contraction of the heart

37
Q

What prevents inversion of valves during systole?

A

The papillary muscles on the inner walls of the ventricles that attach to the cusps of the mitral and tricuspid valves via the chordae tendineae

38
Q

What happens at the atrioventricular node to the action potential?

A

It is delayed for 120ms to allow for atria to finish contraction before the ventricles contract

39
Q

What are the 7 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.
40
Q

What side of the heart is represented on a wiggers diagram?

A

The left side of the heart, would be at a lower pressure if it represented the right side of the heart.

41
Q

What is represented on a wiggers diagram?

A

Aortic pressure, L. ventricular pressure, L atrial pressure, L ventricular volume, electrocardiogram, phonocardiogram.

42
Q

What happens in phase 1 of the wiggers diagram?

A

Atrial contraction - A wave on atrial pressure line as increase in atrial pressure due to atrial systole. P wave in ECG signifies onset of atrial depolarisation. At the end of phase 1 ventricular volumes are maximal (end diastolic volume)

43
Q

What is end diastolic volume?

A

The maximum volume of the ventricles (120ml). Occurs after atrial contraction.

44
Q

What is phase 2 on the wiggers diagram?

A

Isovolumetric contraction - intraventricular pressure exceeds atrial pressure and mitral valve shuts, causing C wave on atrial pressure line and the Lub heart sound. Rise in ventricular pressure as ventricle contracts. Isovolumetric as no change in volume as all valves are closed. QRS complex signifies ventricular depolarisation.

45
Q

What is phase 3 on the wiggers diagram?

A

Rapid ejection - aortic valves open and ejection from the ventricles begins. Pressure in the ventricles and aorta increases. Atrial pressure decreased (X descent) even though blood is still flowing in as ventricular contraction pulls the base of the atria downwards . Rapid decrease in ventricular volume.

46
Q

What is phase 4 on wiggers diagram?

A

Reduced ejection - repolarizatoin of ventricle leads to a decline in tension and the rate of ejection begins to fall. Atrial pressure gradually rises due to venous return from the lungs, this is called the V wave. Ventricular repolarisation depicted by the T- wave of ECG.

47
Q

What is phase 5 on wiggers diagram?

A

Isovolumetric relaxation - intraventricular pressure falls below that of the aortic pressure. Brief backflow of blood before the aortic valve shuts which causes second dub heart sound . Diacritic notch in aortic pressure curve. Rapid decline in ventricular pressure as myocardium relaxes. Volume of the ventricles remains constant as all valves are closed. This is the end systolic volume.

48
Q

How is stroke volume calculated?

A

End diastolic volume (EDV) - end systolic volume (ESV) = stroke volume
Stroke volume is usually 70-80ml

49
Q

What is phase 6 on wiggers diagram?

A

Rapid filling - mitral valve opens. Fall in atrial pressure shown as a Y descent. Blood rapidly moves from the atria into the ventricles. May hear a third heart sound due to rapid ventricular filling.

50
Q

What is phase 7 on the wiggles diagram?

A

Reduced filling - rate of filling of the ventricles slows (diastasis) as ventricles reach its inherent relaxed volume. Further filling driven by venous pressure. Ventricles are 90% full by the end of reduced filling.

51
Q

What is stenosis?

A

When valves do not open enough, causing obstruction to blood flow when valves are normally open

52
Q

What is regurgitation?

A

When valves cannot close completely, resulting in back leakage when valve should be closed.

53
Q

What causes aortic valve stenosis?

A

Degeneration ( senile calcification/fibrosis )
Congenital (bicuspid form of valve)
Chronic rheumatic fever (antibodies attack cells of the heart, causing inflammation and commissural fusion)

54
Q

What are the consequences of aortic valve stenosis?

A

Blood flow is restricted

  • increased left ventricular pressure, LV hypertrophy
  • Left sided heart failure, syncope, angina.
  • shear stress on erythrocytes, microangiopathic haemolytic anaemia
55
Q

What sound is produced by an aortic valve stenosis?

A

Crescendo-decrescendo murmur between S1 and S2

During ventricular contraction

56
Q

What are the causes of aortic valve regurgitation?

A
  • aortic root dilation ( leaflets are pulled apart)

- valvular damage (endocarditis rheumatic fever)

57
Q

Wha are the consequences of aortic regurgitation?

A

Blood flows back into LV during diastole, resulting in an increased stroke volume. Systolic pressure increased and the diastolic pressure decreases. Bounding pulse which may present head bobbing and Quinke’s sign. LV hypertrophy.

58
Q

What is the sound produced by an aortic valve regurgitation?

A

Early decrescendo diastolic murmur ( just after S2)

59
Q

What causes mitral valve regurgitation?

A
  • Myxomatosis degeneration weakens the connective tissue of the valves and can lead to a prolapse.
  • damage to papillary muscle after a heart attack.
  • left sided heart failure leading to LV dilation which can stretch valve
  • rheumatic fever can lead to leaflet fibrosis which disrupts the seal formation
60
Q

What are the consequences of mitral valve regurgitation?

A

Blood leaks back into the LA. increased preload as more blood enters the LV in subsequent cycles. LV hypertrophy

61
Q

What sound is produced by mitral valve regurgitation?

A

A holosystolic murmur

62
Q

What causes mitral valve stenosis?

A

Rheumatic fever

Commissural fusion of the valve leaflets

63
Q

What are the consequences of mitral valve stenosis?

A

Increased LA pressure

  • pulmonary oedema, dyspnea, pulmonary hypertension. This results in RV hypertrophy.
  • LA dilation leading to atrial fibrillation and thrombus formation
  • LA dilation may also cause oesophagus compression resulting in dysphagia
64
Q

What is the average weight of a typical human heart?

A

350g

65
Q

Which valve in the human heart typically has 2 cusps?

A

Mitral valve (left atrioventricular valve)

66
Q

Which muscles help prevent the inversion of the mitral and tricuspid valve during systole.

A

Papillary muscles via chordae tendineae

67
Q

In which structure are the pacemaker cells of the heart located?

A

In the sink atrial node

68
Q

Which heart sounds are made from the closure of the aortic and pulmonary valves?

A

S2

69
Q

What is the correct state of the valves during phase 2 of the cardiac cycle? (Isovolumeric contraction)

A

Aortic and pulmonary are closed

70
Q

Which type of anaemia can result form aortic valve stenosis?

A

Microangiopathic haemolytic anaemia.

71
Q

What condition would result from mitral valve stenosis?

A

Dysphasia

Due to dilation of the left atrium compressing the oesophagus

72
Q

What are the resistance vessels?

A

The arterioles. Can vasoconstrict to increase the TPR, thereby restricting blood flow.

73
Q

What are the Capacitance vessels?

A

The veins. Enable system to vary amount of blood pumped around the body.

74
Q

At rest, where is most of the blood pumped to?

A

The GI tract

75
Q

When we exercise where is most of our blood pumped to?

A

The muscles

76
Q

Describe the structure of cardiac muscle

A

Discrete cells but interconnected electrically by gap junctions (functional syncytium). This allows the AP to travel through the entire myocardium.

77
Q

How does the AP spread through the ventricles of the heart?

A

Spreads down the septum of the heart from the sink atrial node. Next spreads through the ventricular myocardium from inner endocardium surface to outer epicardial surface via purkinje fibres

78
Q

How long is the total duration of a cardiac cycle at rest?

A

0.9s (67 bpm)

79
Q

When our Heart rate increases, what stage of the cardiac cycle changes?

A

Diastole becomes shorter

Systole does not change

80
Q

How much of the end diastolic volume of the ventricles does atrial contraction account for?

A

Final 10%. Initial 90% is passive filling.

81
Q

What causes the s1 heart sound?

A

The closure of the atrioventricular valves.

82
Q

What heart sound do we hear in a patient with mitral valve stenosis

A

Snap as valve opens after S2. Diastolic Murmur

CVS (9 decks)

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