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BMS 242 - CVS respiratory > Cardiac cycle > Flashcards

Cardiac cycle Flashcards

1
Q

What are the 4 major stages of the cardiac cycle?

When does each stage occur?

A

1) INFLOW phase (into the ventricles)
2) ISOVOLUMETRIC CONTRACTION
3) OUTFLOW phase (out of the ventricles)
4) ISOVOLUMETRIC RELAXATION

Stages 1 and 4 - during DIASTOLE
Stages 2 and 3 - during SYSTOLE

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2
Q

What happens in the inflow phase of the cardiac cycle?

A

Blood ENTERS the heart

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3
Q

What happens in the isovolumetric contraction of the cardiac cycle?

A

Contraction where the VOLUME of the heart stays the SAME

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4
Q

What happens in the outflow phase of the cardiac cycle?

A

Blood from the heart to the lungs or systemic system

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5
Q

What happens in the isovolumetric relaxation of the cardiac cycle?

A

Relaxation of the heart where the VOLUME of the ventricles stays the SAME

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6
Q

What is diastole?

What happens during diastole?

A

Heart RELAXING

Ventricles FILL with blood

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7
Q

What is systole?

A

Heart CONTRACTING

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8
Q

Describe the movements through the valves of the heart

A

Passive

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9
Q

What is LVDEV?

A

Left ventricular diastolic end volume

Volume in the left ventricle at the end of diastole

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10
Q

What is LVSEV?

A

Left ventricular systolic end volume

Volume in the left ventricle at the end of systole

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11
Q

What initiates the cardiac cycle?

A

P wave

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12
Q

How do both atria contract simultaneously?

A

Fast conduction velocity in the BRACHMNN’S BRANCH - takes the electrical signal to the left atria

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13
Q

What does atrial contraction cause?

A
  • Increase in blood pressure in both atria
  • Forcing the valves open
  • Squeezing the blood into the ventricles
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14
Q

How does 80% of blood flow into the ventricles occur?

How does the rest occur?

A

PASSIVELY

Rest occurs through ATRIAL KICK

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15
Q

How does blood flow into the ventricles occur passively?

A
  • Gravity

- Elastic recoil

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16
Q

What can reduce/extinguish atrial kick?

A

Atrial fibrillation - struggle during exercise

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17
Q

What happens after atrial contraction is complete?

What does this cause?

A

Atrial pressure falls:

Causes a pressure gradient REVERSAL across AV valves

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18
Q

What does the pressure gradient reversal across the AV valves cause?

A
  • Small backflow of blood
  • Valves float upwards before closure (pre-position)
  • Valves close
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19
Q

What are the ventricular volumes in phase 1 (inflow phase)?

Why?

A

MAXIMAL (EDV)

Blood has just been pushed into the ventricles from the atria

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20
Q

What is the LEDV value?

What does this represent?

A

120ml

Represents the VENTRICULAR PRELOAD (stretching of the cells in the ventricles)

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21
Q

What happens to the ventricular preload during exercise?

A

It INCREASES:

Ventricles can contract harder to push the blood out QUICKER

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22
Q

What are the end-diastolic pressures?

A

LV - 8-12mmHg

RV - 3-6mmHg

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23
Q

Why is the end-diastolic pressure in the RV lower than in the LV?

A

1) RV walls are THINNER

2) Pulmonary circuit:
- Alveoli cell walls are one cell thick, with fenesta in between the cells

  • Low pressure so that the plasma doesn’t get pushed out of the vessels and fill the alveoli with fluid –> pulmonary oedema
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24
Q

What happens in phase 2 of the cardiac cycle (isovolumetric contraction)?

A
  • ALL valves are CLOSED
  • Begins with the appearance of QRS complex in the ECG
  • Depolarisation of the ventricles
  • Rate of pressure development in the ventricles becomes maximal rapidly
  • AV valves close when the ventricular pressure is more than the atrial pressure
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25
Q

What does the QRS complex in the ECG represent?

A

Ventricular DEPOLARISATION

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26
Q

What does ventricular depolarisation trigger?

A

1) Excitation-contraction coupling
2) Myocyte contraction
3) Rapid increase in intraventricular pressure
4) Closure of the AV valves

ALSO

27
Q

As well as an increase in pressure and closure of the valves, what else does ventricular contraction trigger?

What does this cause?

A

Contraction of the PAPILLARY muscles with there cordae tendinae

Causes tension on the AV valve leaflets - preventing them from bulging back too far into the atria and becoming incompetent?

28
Q

Describe the contraction of phase 2 of the cardiac cycle

A

ISOVOLUMETRIC

Rapid increase in pressure WITHOUT a change in ventricular volume (aortic and pulmonary valves are closed)

29
Q

What is the T wave on the ECG?

A

Repolarisation of the ventricles

30
Q

What causes the ‘C-wave’ in the LAP wave?

A

Slight bulging back of the AV valve into the left atrium - increasing the pressure

31
Q

What happens during phase 3 of the cardiac cycle?

A
  • Aortic and pulmonary valve OPEN

- Ejection of the blood from the ventricles

32
Q

When does ejection from the ventricles occur?

A

When the pressure in the ventricles EXCEEDS the pressure in the aorta/pulmonary artery

33
Q

What heart sound represents the opening a HEALTHY aortic/pulmonary valve?

In a heart with DISEASED valves?

A

Healthy - NO heart sounds

Diseased valved - Heart murmers (can hear the valves close)

34
Q

When is maximum outflow velocity from the ventricles acheived?

A

EARLY in ejection phase

When maximal aortic and pulmonary artery pressures are acheived

35
Q

What happens to the left atrial pressure during ejection from the ventricles?

Why?

A
  • Initially DECREASE (atrial base is pulled downwards as it is connected to the ventricle - expands the atrial chamber)
  • THEN, atrial pressure INCREASE - due to blood flow into the atria from the venous inflow tracts
  • Pressure continues to rise until the AV valve open at the end of phase 4
36
Q

What occurs in phase 4?

A

ISOMETRIC RELAXATION:
- Pressure DECREASE in the ventricles but no blood flow in the ventricles

  • When intraventricular pressures fall sufficiently - aortic and pulmonary valves close ABRUPTLY
  • Blood from the vessels slightly pushes back
37
Q

What is the aortic and pulmonary valve closure associated with?

What does this cause?

A

1) A small BACKFLOW of blood into the VENTRICLES

Causes a characteristic NOTCH (diacrotic NOTCH) in the aortic and pulmonary artery pressures

2) And THEN, increase in pressure - diacrotic WAVE
3) Followed by a slow decline in pressure

38
Q

What is the rate of pressure decline in the ventricles determined by?

What is this REGULATED by?

A

The RATE of RELAXATION of the cardiac myocytes (muscle fibres)

Regulated by - SARCOPLASMIC RETICULUM that are responsible for rapidly re-sequestering calcium following contraction

39
Q

What is the ability of the cardiac myocytes to relax called?

A

Lusitrophy

40
Q

What happens to the ventricular pressures in phase 5?

A

Decrease WITHOUT volume changes (valves are closed)

41
Q

What is the volume of blood that remains in the ventricle after contraction called?

What is this volume?

A

End-systolic volume

~50ml

42
Q

What happens to the ESV during excercise?

A

Exercising

43
Q

What is the ejection fraction?

A

The amount of blood ejected from the heart

44
Q

What is the stroke volume?

A

The difference between the END-DIASTOLIC and END-SYSTOLIC volume

About ~70ml

45
Q

What is LAP?

What happens to the LAP during phase 4?

A

Left atrial pressure

Continues to rise - due to venous return from the lung

46
Q

What is the peak LAP determined by?

A

The v-wave on the LAP wave

47
Q

What is phase 6 of the cardiac cycle?

A

RAPID filling of the ventricles

48
Q

What happens as the ventricles continue to relax?

A
  • Intraventricular pressures will eventually FALL below their respective atrial pressures
  • AV valves RAPIDLY OPEN and PASSIVE ventricular filling begins
49
Q

Why does the intraventricular pressure continue to briefly fall, even when there is blood flow in from the atria?

A

Cardiac myocytes in the ventricles are still undergoing relaxation

50
Q

When does the pressure in the ventricles begin to rise?

A

Once the AV valves are open and the ventricles are completely relaxed

51
Q

What comes immediately after the v-wave on the LAP wave?

Why?

A

y-decent of the LAP

Opening of the mitral valve causes a rapid fall in LAP

52
Q

What is the sound of ventricular filling?

When is this different?

A

Normally silent

Sound normally heart during RAPID heart filling:
- Represents the tensing of the chordae tendineae and the AV ring

53
Q

What happens when the ventricles fill with blood and expand?

A
  • LESS compliant

- Intraventricular pressure RISE

54
Q

What does the rise in intraventricular pressure when the ventricles fill with blood?

What does this cause?

A

Reduces the pressure gradient across the AV valves

Reduces the rate of filing late in diastole

55
Q

What happens to the pressures in the atria and aorta when the ventricles fill with blood?

A

Their pressures fall

56
Q

What are the heat sounds?

What produces them?

A

S1 - Closure of the mitral and triscupid valves

S2 - Closure of the aortic and pulmonary sounds

S3 - Early diastolic sound. Normally silent

57
Q

Why is the S1 sound normally split?

A

Mitral valve normally closes slightly BEFORE the tricuspid valve

58
Q

Which heart sound is the longest?

A

S1

59
Q

Which blood vessel valve closes first in S2?

A

Aortic valve

60
Q

What does the S1 sound correspond to?

A

END of diastole

BEGINNING of systole

61
Q

What does the S2 heart sound correspond to?

A

END of systole

62
Q

What does the S3 heart sound correspond to?

A

Rapid entry of blood from the atrium to the ventricle

63
Q

Describe the left and right asynchrony?

A

RIGHT atrial first
LEFT ventricle first
RIGHT ventricular ejection first

BMS 242 - CVS respiratory (15 decks)

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