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BMS242 CVS Phys > L11 - Cardiac Cycle > Flashcards

L11 - Cardiac Cycle Flashcards

1
Q

Define the cardiac cycle

A

The series of mechanical and electrical events which occur and repeat with each beat of the heart

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2
Q

4 phases (brief) of the cardiac cycle

A

Innflow of blood
Isovolumetric contraction
Outflow of blood
Isovolumetric relaxation

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3
Q

What does isovolumetric mean

A

Contraction or relaxation of the chambers with both of the valves shut, lead to no change in volume but a change in pressure is seen

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4
Q

What ECG wave represents atrial depolarisation

A

P wave

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5
Q

Since the SA node is found in the right atrium, does the right ventricle contract before the left atrium, why?

A

No both conduct simulataneously thanks to the fast conduction velocity of the impulse via Bachmans bundle

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6
Q

What occurs when the atria contract

A

Pressure in the atria increases and blood is squeezed into the ventricles

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7
Q

How much of the blood entering the ventricles is passive, how much is down to the contraction of the atria

A

80% passive, around 10% from atrial contraction

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8
Q

What is the contraction of the atria also known as

A

The atrial kick

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9
Q

What occurs once the atria have finished contraction

A

Atrial pressure falls and a pressure gradient reversal occurs across the AV valves causing the valves to float upward before closure

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10
Q

What occurs to the AV valves after the atria have finished contraction

A

Pressure gradient reversal across the AV valves causes them to float upwards before they close

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11
Q

At phase 1 what is maximum

A

The volumes of the ventricles

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12
Q

When do end diastolic volume (what phase)

A

1

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13
Q

What is end disastolic volume

A

The maximum volume of blood in the ventricles

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14
Q

What is LVEDV

A

Left ventricle end diastolic volume

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15
Q

What is the typical LVEDV and what does this represent

A

120ml

The ventricular preload

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16
Q

What is the ventricular preload

A

The intial strectching of the cardiomyocytes prior to contraction

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17
Q

Typical end diastolic pressure of the Lv

A

8-12 mmHg

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18
Q

Typical end diastolic pressure of the RV

A

3-6 mmHG

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19
Q

Why is the end diastolic pressure of the RV lower than the LV

A

Wall of the epithelium is thin in pulmonary circulation, gaps between the capillary endothelial cells to allow movement of substances.
If pressure was too high fluid would be forced through the gaps and into the lungs - would cause oedema

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20
Q

What does the QRS complex represent - what phase is this this the beginning of

A

Ventricular depolarisation, marks the start of phase 2

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21
Q

What is the state of all of the valves in phase 2

A

All of the valves are closed

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22
Q

What does ventricular depolarisation trigger

A

Excitation, contraction coupling

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23
Q

What can be said about dP/dt during phase 2

A

Maximal early in phase 2

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24
Q

When do the AV valves close

A

When the intraventricular pressure exceeds the atrial pressure

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25
Q

What also contracts during ventricular contraction, what does this do and prevent

A

Contraction of the paillary muscles, causing tension in the cordae tendinea attached to the valve leaflets. The tension in the AV valve leaflets prevent them from bulging backward and inverting

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26
Q

What causes the first heart sound

A

The closing of the AV valves

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27
Q

Why does the first heart sound compose of two parts? What is the gap between the two sounds

A

Because mitral valve closes slightly earlier than the triscuspid valve

28
Q

Which side of the heart is the tricuspid

A

tRiscuspid RIGHT

29
Q

Which side of the heart is the mitral valve

A

mitraL LEFT

30
Q

Phase 3 is also known as

A

Isovolumetric contraction

31
Q

What two valve movements does phase 3 occur between

A

The closure of the AV valves and then the openig of the pumonary/aortic valves

32
Q

Because their is no change in volume, when contractign what happens

A

Rapid rise in pressure

33
Q

During isovolumetric contraction what determines the dP/dt

A

Rate of contraction of the muscle fibres which is in turn governed by mechanisms governing excitation contraction coupling

34
Q

What causes the c wave in LAP, when does this occur

A

Bulging back of mitral valve leaflets into the left atrium ==> causes the volume here to decrease slightly

35
Q

What is the state of the two valves during phase 4

A

Aortic and pulmonary valves open

The AV valves remain closed

36
Q

At what point does ejection begin

A

When the intraventricular pressure exceeds the pressure in the aortic and pulmonary arteries which then causes the respective valves to open

37
Q

When is MAX outflow velocity reached

A

Early in the ejection phase

38
Q

Are any heart sounds made during ejection

A

No opening of the healthy valves is a normally silent process

39
Q

What occurs to LAP during ejection (phase 4)

A

Initially decreases as the atrial base is pulled downward expanding the atrial chamber

40
Q

What occurs during phase 5

A

Isovolumetric relaxation

41
Q

What phase does isovolumetric relaxation occur in

A

5

42
Q

When do the aortic and pulmonary valves close

A

When the intraventricular pressure has fallen sufficiently

43
Q

Does the aortic or pulmonary valve close first

A

Aortic closes first

44
Q

What causes the second heart sound

A

The closing of the aortic and pulmonary valves

45
Q

What is the closure of the aortic and pulmonary valve associated with

A

A small backflow of blood into the ventricles and a characterisic notch (dicrotic notch)

46
Q

What is the rate of pressure decline in the ventricles determined by, what is this known as

A

Determined by the rate of relaxation of the ventriuclar muscle, known as leuistropy (rate of relaxation)

47
Q

What is leuisitropy regualted by

A

Regulated by the sarcoplasmic reticulum which is responsible for re-sequestering Ca ions following contraction

48
Q

When all of the valves have closed at the muscle is relaxing what does this cause

A

Decrease in pressure but no change in volume

Isovolumetric releaxation

49
Q

Once the aortic valve has shut what is the volume of blood left known as, what is a typical value for this

A

Left ventricular end systolic volume

50ml

50
Q

What is the equation for stroke volume, show how a typical stroke volume is 50 mls

A

LVEDV - LVESV = SV

120 - 50 = 70 mls

51
Q

During isolvolumetric relaxation of the ventricles what is happening to LAP

A

Continuing to rise due to venous return of the blood

52
Q

Phase 6 is known as

A

Rapid filling

53
Q

Which phase is rapid filling

A

6

54
Q

When/how does ventricular filling begin

A

As ventricles relax intraventricular pressure falls below the pressure in the atria this causes the AV valves to open and blood to flow into the ventricles

55
Q

Why does intraventricular pressure continue to fall despite them filling

A

They are still relaxing

56
Q

What occurs to LAP when the mitral valve opens

A

Rapid fall

57
Q

When is the peak of the LAP, what is this called, what occurs after

A

Peak just before the mitral valves open known as the v wave, followed by the y-descent of the LAP

58
Q

Where is a similar V and Y wave and descent seen in the body

A

Found in the right atrium and the jugular vein

59
Q

What can be said about S3

A

Usually silent

60
Q

What would some reasons for a sound being heard at S3 be

A

Tensing of the chordae tendinae or AV ring

Could be the turbulent flow of blood back into the ventricles

61
Q

What occurs as the ventricles continue to fill

A

They become less compliant and the intraventricular pressure rises, this reduced the pressure gradient across the AV valves so rate of filling is reduced

62
Q

What % of ventricular filling is passive

A

90%

63
Q

A wave in LAP represents

A

Atrial systole

64
Q

What is S1

A

Closure of the mitral and tricuspid valve, marks the end of diastole and beginning of ventricular systole

65
Q

What is S2

A

Closure of the aortic and pulmonary valves at the end of systole

66
Q

What is S3

A

Low pitched rapid entry of blood from the atria to te ventricles

67
Q

What part of the stephoscope is S3 best heard through

A

The bell

BMS242 CVS Phys (12 decks)

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