3: The cardiac cycle Flashcards Preview

Cardiovascular Week 1 & 2 2016/17 > 3: The cardiac cycle > Flashcards

Flashcards in 3: The cardiac cycle Deck (43)
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1
Q

When do cardiac valves produce a sound?

A

When they shut (not when they open!)

2
Q

Give a simple definition of the cardiac cycle.

A

All the events occuring from the beginning of one heart beat to the beginning of the next

3
Q

Give a technical definition of the cardiac cycle.

A

The orderly depolarisations / repolarisations causing atrial / ventricular contractions and relaxations.

4
Q

Put simply, what happens during diastole?

A

The heart chambers relax and are filled with blood

5
Q

Put simply, what happens during systole?

A

The heart ventricles contact and pump blood into:

a) the aorta
b) the pulmonary artery

6
Q

How long is diastole compared to systole?

A

Diastole is about twice as long as systole

7
Q

Name the five events which take place during the cardiac cycle.

A
  1. Passive Filling
  2. Atrial Contraction
  3. Isovolumetric Ventricular Contraction
  4. Ventricular Ejection
  5. Isovolumetric Ventricular Relaxation
8
Q

During the passive filling phase, what is the pressure in the atria and ventricles?

A

Nearly zero

9
Q

During passive filling, which valves open and what flows into the ventricles?

A

1) The AV valves (RA tricuspid valve, LA mitral valve)
2) Venous return from the systemic and pulmonary circulations flows into the ventricles

10
Q

During passive filling, the aortic and pulmonary valves are…

A

closed.

11
Q

How full do the ventricles become simply through passive filling?

A

Around 80% full

12
Q

Which wave on an ECG signals atrial depolarisation?

A

P wave

13
Q

Which interval on an ECG represents the whole of atrial contraction?

A

PR interval

14
Q

Which wave(s) on an ECG signal ventricular depolarisation?

A

QRS complex

15
Q

When does ventricular contraction start on an ECG?

A

After the QRS complex

16
Q

During isovolumetric ventricular contraction, what pressure change occurs in the ventricles?

A

Ventricular pressure rises

17
Q

When do the AV valves shut?

A

When ventricular pressure EXCEEDS atrial pressure

18
Q

In which phase of the cardiac cycle do the AV valves first shut - why?

A

Isovolumetric ventricular contraction

Ventricular pressure exceeds atrial pressure - valves shut to prevent backflow of blood into the atria

19
Q

When is the first heart sound heard in the cardiac cycle - why?

A

Isovolumetric ventricular contraction - because the AV valves shut

20
Q

In the isovolumetric ventricular contraction phase, the AV valves shut - what sound does this produce?

A

First heart sound - LUB

21
Q

During the isovolumetric ventricular contraction phase, the aortic valve is…

A

shut.

22
Q

Why is the ventricular contraction phase “isovolumetric”?

A

Tension (pressure) increases in a closed volume (the ventricle itself)

23
Q

In which phase of the cardiac cycle do the aortic / pulmonary valves open?

A

Ventricular ejection

24
Q

Is a sound produced when the aortic and pulmonary valves open?

A

No - silent event

25
Q

Which volume is ejected by the ventricles during the 4th phase of the cardiac cycle?

A

Stroke volume

26
Q

Which volume remains after the stroke volume has been ejected in the 4th phase of the cardiac cycle?

A

End systolic volume (ESV)

27
Q

Write an equation for stroke volume.

A

Stroke volume = end diastolic volume - end systolic volume

28
Q

What occurs after the ejection of the stroke volume?

A

Aortic pressure rises

29
Q

Which wave on an ECG signals ventricular repolarisation?

A

T wave

30
Q

After the ejection of blood from the ventricles, when ventricular pressure falls, what happens?

A

The aortic and pulmonary valves SHUT

31
Q

Why is the second heart sound produced?

A

Ventricular pressure falls below aortic pressure and the valves shut

32
Q

What is the second heart sound and when does it occur?

A

DUB - at the end of ventricular ejection

33
Q

When does isovolumetric ventricular relaxation start?

A

When the aortic/pulmonary valves close

34
Q

Why is ventricular relaxation “isovolumetric”?

A

Tension (pressure) falls in a closed volume (the ventricle)

35
Q

What happens when ventricular pressure falls below atrial pressure during the 5th phase of the cardiac cycle?

A

AV valves open

36
Q

When the AV valves open in the 5th phase of the cardiac cycle, is any sound produced?

A

No - opening of valves is silent

37
Q

The first heart sound occurs when the AV valves ___ and signals the beginning of ___.

A

shut , systole

38
Q

The second heart sound occurs when the aortic / pulmonary valves ___ and signals the beginning of ___.

A

close , diastole

39
Q

Where would you place your stethoscope to auscultate the aortic valve?

A

Right sternal edge, 2nd intercostal space

40
Q

Where would you place your stethoscope to auscultate the pulmonary valve?

A

Left sternal edge, 2nd intercostal space

41
Q

Where would you place your stethoscope to auscultate the mitral valve?

A

Mid-clavicular line, 5th intercostal space

or wherever the apex beat is in reality

42
Q

What happens after isovolumetric ventricular contraction?

A

Passive filling (the heart begins a new cardiac cycle)

43
Q

What prevents arterial pressure from falling to zero during diastole?

A

Elastic recoil