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ESA2 LKM > CVS - cardiac cycle > Flashcards

CVS - cardiac cycle Flashcards

1
Q

What is the role of capacitance vessels?

A

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

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2
Q

What is the role of resistance vessels?

A

Restrict blood flow to drive supply to hard to perfuse areas of the body.

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3
Q

Define systole

A

Contraction and ejection of blood from ventricles

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4
Q

Define diastole

A

Relaxation and filling of ventricles

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5
Q

Heart muscle is made from discrete cells. How are they electrically interconnected?

A

Gap junctions (part of intercalated discs along with adherens-type junctions for anchorage of cells and actin filaments).

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6
Q

Cardiac myocyte action potential lasts a relatively long time, so it lasts for the duration of a single heart beat. Approximately how long does it last?

A

280ms

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7
Q

Which valves are attached to papillary muscles via chordae tendinae? What is the purpose of these structures?

A

Tricuspid and mitral valves. Prevents inversion of valves on systole.

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8
Q

How long does the AV node delay excitation for?

A

~120ms

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9
Q

Which direction does ventricular myocardium contract during systole?

A
  1. Endocardial to epicaridal

2. Apex to base

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10
Q

What are the 7 stages of the cardiac cycle?

A
  1. Atrial contraction
  2. Isovolumetric contraction
  3. Rapid ejection
  4. Reduced ejection
  5. Isovolumentric relaxation
  6. Rapid filling
  7. Reduced filling
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11
Q

Approximately how long is systole?

A

~0.35s

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12
Q

A Wiggers diagram typically plots which side of the heart?

A

Left side of the heart

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13
Q

What is meant by end diastolic volume?

A

It is at the end of atrial contraction when the ventricles containe their maximum volume of blood.

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14
Q

What happens during phase 1 (atrial contraction)?

A
  1. Atrial pressure rises due to atrial systole. This is called the “A wave”
  2. Atrial contraction accounts for final ~10% of ventricular filling (varies with age and exercise)
  3. P wave in ECG signifies onset of atrial depolarisation
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15
Q

What is a typical end-diastolic volume?

A

~120ml

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16
Q

What happens during phase 2 (isovolumetric contraction)?

A
  1. Mitral valve closes - as ventricular pressure exceeds atrial pressure
  2. Rapid rise in ventricular pressure as ventricle contracts
  3. Closing of mitral valve creates the “C wave” in the atrial pressure curve.
17
Q

Describe the state of the valves in the isovolumetric contraction/relaxation phases

A

All valves are closed.

18
Q

What causes S1 - the first heart sound?

A

Closing of the mitral and tricuspid valves

19
Q

When does the rapid ejection phase start?

A

When intraventricular pressure exceeds aortic pressure, causing the aortic valve to open.

20
Q

What causes the X descent in atrial pressure?

A

Pulling of the atrial base downwards that occurs as the ventricle contracts.

21
Q

Whilst rapid ejection is occurring, what else is simultaneously occurring in the atria?

A

Blood is continuing to flow into the atria from their respective venous inputs.

22
Q

What causes the rate of ejection to begin to fall and therefore causes phase 4 (reduced ejection)?

A

Repolarisation of the ventricle which leads to a decline in tension.

23
Q

What causes the “V wave” of atrial pressure?

A

Atrial pressure gradually rises due to the continued venous return from the lungs.

24
Q

What causes the aortic valve to close?

A

The brief backflow of blood that occurs when intraventricular pressure falls below aortic pressure.

25
Q

What causes the “dicrotic notch” in aortic pressure?

A

Closure of the aortic valve

26
Q

What is end systolic volume (ESV)?

A

The volume of blood in the ventricles at the end of systole

27
Q

How do you calculate the stroke volume?

A

EDV-ESV

28
Q

What is a typical stroke volume?

A

~80ml

29
Q

What is the cause of S2 (the second heart sound)?

A

Closure of the aortic and pulmonary valves.

30
Q

What causes the “Y descent” in atrial pressure?

A

Fall in atrial pressure due to the opening of the mitral valve.

31
Q

What causes the mitral valve to open and the rapid filling phase to begin?

A

Fall of intraventricular pressure below that of atrial pressure. This is PASSIVE FILLING of the ventricle, the atria are not contracting.

32
Q

S3 (third heart sound) is sometimes present. What causes it? When can it be heard?

A

It’s caused by ventricular filling (though this is normally silent). The S3 sound is normal in children but can be sign of pathology in adults.

33
Q

What causes ventricular filling to slow down?

A

Diastasis (slowing down of rate of filling) occurs as the ventricle reaches its inherent relaxed volume. Further filling is driven by venous pressure.

34
Q

How full are the ventricles (at rest) at the end of phase 7 (the reduced filling phase)?

A

~90%

ESA2 LKM (45 decks)

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