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Block 4 > Physiology: The heart as a pump > Flashcards

Physiology: The heart as a pump Flashcards

1
Q

How are RH and LH (two independent pumps) connected?

A

Connected in series

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2
Q

Two phases of cardiac cycle

A
  • Filling (diastole)

- Ejection phase (systole)

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3
Q

Diastole

A

Fills passively due to pressure gradient from great veins

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4
Q

Systole

A

Heart actively contracts

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5
Q

Diastole is a passive event with the exception of?

A

Exception of the final part of ventricle filling which requires some contraction.

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6
Q

Ventricular diastole lasts for?

A

2/3 of the cycle (longer)

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7
Q

Atrial systole precedes ventricular systole

A

True

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8
Q

Systole begins slightly after ejection

A

False, it begins slightly before the beginning of ejection.

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9
Q

If atrial systole doesn’t occur, can the heart still function?

A

Yes, because the ventricle is already ~80% full

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10
Q

What specifically produces contractions?

A

Ventricular myocardium, particularly in the left ventricle

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11
Q

Which contraction should precede the other?

A

Atrial contraction should precede ventricular contraction (accounting for final filling stage of the ventricle)

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12
Q

Synchronous contraction is necessary for each chamber

A

True

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13
Q

Where are valves located?

A

Valves are located at input and output of ventricles.

Atria have no valves at entry and are thin walled holding vessels.

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14
Q

Stimuli of ventricles?

A

Ventricles need regular stimuli to contract (do not come from extrinsic nerves).

Autoactive and intrinsic pacemaker regions (primarily SA node) are the stimuli.

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15
Q

List the stages of depolarisation in the heart

A
  1. SA node
  2. AV node
  3. AV bundle
  4. Right and left bundle branches
  5. Purkinje fibres
  6. Ventricular myocardium.
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16
Q

Heart can beat without which node?

A

SA node.

Because AV node can act as pacemaker instead.

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17
Q

SA node is a muscle fibre acting as a?

A

Conducting fibre

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18
Q

Why is there a delay from atria to ventricles?

A

Because the boundary is non-conducting tissue.
The AP takes some time to get through AV node (100 ms).

Once they do, AP’s propagate through to purkinje fibres beginning with AV bundle which then divide into right and left bundle branches.

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19
Q

What are Purkinje fibres?

A

Rapidly conducting muscle fibres.

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20
Q

Once action potential reach the terminal purkinje fibres, how long does it take to contract the terminal ventricular myocardium?

A

50ms

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21
Q

Mitral valve opens when?

A

Opens during filling (LA and LV) once LA pressure exceeds LV

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22
Q

How long are the delays between SA node and AV node?

A

100 ms

23
Q

Aortic valve is pushed open once?

A

Once LV pressure exceeds aortic pressure

24
Q

Ventricles contracting push against which valve?

A

AV valve

25
Q

Valvular openings and closing are all?

A

Passive processes in response to pressure changes

26
Q

P wave represents?

A

Atrial depolarisation immediately after SA depolarisation.

27
Q

QRS complex represents?

A

Rapid depolarisation of ventricles.

28
Q

How long is delay between SA depolarisation (P wave) and rapid depolarisation of ventricles (QRS complex)?

A

100ms

29
Q

QRs complex shows short spike because?

A

Depolarisation of ventricles occurs almost simultaneously.

30
Q

T wave represents?

A

Ventricular repolarisation (not precisely simultaneously)

31
Q

Ventricular pressure varies enormously.

A

True

32
Q

Atrial pressure varies enormously.

A

False, it is quite stable.

33
Q

Aortic pressure remains low.

A

False, it remains high because of significant resistance in arterioles and capillaries.

34
Q

Atrial pressure is just greater than ventricles just before?

A

Just before SA node depolarisation.

35
Q

As soon as ventricular pressure surpasses atrial, the AV valve between them closes, creating?

A

Creates turbulence (first heart sound - very distinct).

36
Q

Isovolumetric contraction

A

Short period where ventricular muscles contracting but volume is not changing.

Little increase in pressure until ventricular pressure surpasses the aortic pressure in which the aortic valve opens up.

37
Q

Rapid ejection from ventricle occurs until?

A

Aortic pressure exceeds ventricular pressure once more.

38
Q

What is the second sound in heart beat?

A

This is when aortic and pulmonary artery valves close

39
Q

Atrial systole activity

A

Late ventricular diastole, ventricular filling.

Passive flow of blood into left atrium (and left ventricle through mitral valve).

SA node depolarizes - wave of depolarisation sweeps over atria (which then contracts).

40
Q

Isovolumetric contraction activity?

A
  • Ventricular contraction
  • Ventricular pressure rises
  • Atrioventricular valve quickly closes
  • When ventricular pressure exceeds aortic pressure; aortic valve opens.
41
Q

Ventricular ejection activity?

A
  • Ejection most rapid during early part.
  • Terminated by the end of ventricular contraction
  • Ventricular pressure falls rapidly and aortic valve closes.
42
Q

Isovolumetric ventricular contraction activity?

A
  • All valves closed
  • Ventricular pressure falls
  • Aortic run-off is much less rapid, being dependent on peripheral resistance, aortic pressure falls much less rapidly than ventricular pressure.
43
Q

Early ventricular diastole activity?

A
  • Ventricular filling

- Ventricle is >80% full prior to atrial systole (which is during late ventricular diastole - Phase 1

44
Q

Every time the heart contracts, every cardiac muscle cell is?

A

Is recruited with no recovery times.

45
Q

Which metabolism occurs in cardiac muscle cells?

A

Aerobic metabolism - highly efficient

46
Q

Up to 40% of a myocardial cell’s volume is made up of?

A

Mitochondria (the O2-dependent energy organelles), compared to ~5% in the case of skeletal muscle.

47
Q

why is O2 and nutrients not extractable from blood passing through the heart chambers?

A
  • Endothelial lining of the chambers is not permeable.

- Cardiac muscle wall is too thick for diffusion of oxygen to take place

48
Q

Coronary arteries arise where?

A

Arise from the base of the ascending aorta of at the aortic sinuses.

49
Q

Heart rate is inversely proportional to cardiac cycle

A

True: as HR increases, diastole decreases more than systole, this denies full filling of the ventricles.

Thus, increased HR = decreased stroke volume

50
Q

Blood can only flow through small coronary vessels when?

A

During diastole (coronary arteries on epicardium of heart are not effected).

51
Q

Which muscle layer of heart is more susceptible to ischaemia?

A

Endocardium.

52
Q

Flow through coronary vessels impaired at high heart rate because?

A

Because duration of diastole/cardiac cycle falls.

53
Q

Which ventricle is more susceptible to problems with ischaemia?

A

Left ventricle because it is due to far greater generation of pressure.

54
Q

Flow in right ventricle reflects?

A

Reflects arterial pressure waveform

Block 4 (8 decks)

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