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BIOM20002 - HSF > Lecture 55 - The Cardiac Cycle > Flashcards

Lecture 55 - The Cardiac Cycle Flashcards

1
Q

What prevents the atria and the ventricles from contracting at the same time?
What is this made of?

A

The fibrous skeleton of the heart

It is made of fibrous connective tissue

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2
Q

Compare the pressure in the two sides of the heart

A

Right side: low pressure

Left side: high pressure

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3
Q

Compare the right and left ventricles’ structure

A

Right: thin muscular wall
Left: thick muscular wall

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4
Q

Compare the function of the right and left ventricles

A

Right: pumps deoxygenated blood to the lungs
Left: pumps oxygenated blood to the body

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5
Q

Which circulation has greater resistance?

A

Systemic has greater resistance than pulmonary

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6
Q

What generates the force in the heart?

A

The contraction of the muscular walls of the heart

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7
Q

What are the stages of ventricular systole?

A

Isovolumetric contraction

Ventricular ejection

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8
Q

What are the stages of ventricular diastole?

A

Isovolumetric relaxation

Ventricular filling

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9
Q

Describe the mechanical events of the cardiac cycle

A
  1. Late diastole: chambers filling passively
  2. Atrial systole: blood forced into ventricles
  3. Isovolumetric ventricular contraction
  4. Ventricular ejection
  5. Isovolumetric ventricular relaxation
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10
Q

Describe the electrical events of the cardiac cycle

A
  1. SA node depolarisation
  2. P wave: atrial depolarisation
  3. P-Q segment: conduction through AV node and bundle
  4. Q wave: depolarisation through bundles of His
  5. R wave: depolarisation at apex of heart
  6. S wave: depolarisation through purkinje fibres through ventricle
  7. S-T segment: ventricular contraction
  8. T wave: ventricular repolarisation
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11
Q

Describe what is happening at the SA node

A

Autorhythmic

70 bpm

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12
Q

What controlls the path of conduction through the heart?

A

Insulation

Fibrous skeleton

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13
Q

How is depolarisation conducted from the SA to the AV node?

A

Internodal pathways

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14
Q

Compare depolarisation rates throughout the heart

A

Quick:
• along internodal pathways
• bundles of His

Slow:
• through atria

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15
Q

Why would it be pointless to have sustained contraction of the heart?

How is this overcome?

A

This would not allow the heart to function properly, as the principal function of the heart is to pump blood. Sustained contraction would not allow the heart to refill

The refractory period ensures that the heart can refill between beats.

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16
Q

Describe how an ECG is recorded

A

3 leads placed on the body
Einhoven’s Triangle

Leads detect the direction of flow of electric current.

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17
Q

Describe what we see on an ECG recording.

Draw this

A

Slide 17

P wave
QRS complex
T wave

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18
Q

What does the P wave represent?

A

Atrial depolarisation

19
Q

What does the Q wave represent?

A

Depolarisation of the Bundles of His

20
Q

What does the R wave represent?

A

Spread of depolarisation around the apex of the heart

21
Q

What does the S wave represent?

A

Spread of depolarisation up through the ventricles

22
Q

What does the QRS complex represent as a whole?

A

Ventricular depolarisation

23
Q

What does the T wave represent?

A

Ventricular repolarisation

24
Q

What does a reading above the baseline on an ECG recording indicate?

A

Net movement of charge towards the positive electrode

25
Q

What do we look for in a normal ECG?

A
  • Is the rate regular?
  • Is rhythm regular
  • Are the waves regular?
  • One QRS compex per P wave?
  • Is P-R segment regular in length?
26
Q

What is regular heart rate?

A

60-100 bpm

27
Q

What is atrial fibrillation?

A

Erratic atrial activity; not contracting in a coordinated manner.
Depolarisation does not reach the ventricle each time

28
Q

What is ventricular fibrillation?

A

Erratic electrical activity in the ventricle

Ventricle beating on its own, under the ventricular pacemakers

29
Q

What causes ventricular fibrillation?

A

Damaged muscle of the heart

30
Q

How can ventricular fibrillation be overcome?

A

To restore the normal rhythm, the heart must be in the refractory period. This doesn’t happen during ventricular fibrillation.

De-fibrillator give a high voltage shock to synchronise all the muscle

31
Q

What causes the valves of the heart to open an close?

A

No muscle - it is a passive process.

The pressure changes cause the valves to open and close

32
Q

When do the AV valves open?

A

When pressure in the atria is greater than in the ventricles

33
Q

When do the AV valves close?

A

When pressure in the ventricles is greater than in the atria

34
Q

When do the semilunar valves open?

A

When pressure in the ventricles is greater than in the vessel (aorta, pulmonary trunk)

35
Q

When do the semilunar valves close?

A

When pressure in the ventricles is less than in the vessels (aorta, pulmonary trunk)

36
Q

Which side of the heart has the tricupsid valve?

A

The right side of the heart

37
Q

What is happening during isovolumetric ventricular contraction?

A

The muscle of the ventricles is contracting
However, the valves aren’t open.

The pressure in the ventricles is rising up to 120 mmHg

38
Q

Why does blood flow into the ventricles?

A

Blood has been ejected from the ventricles, and the muscle of the ventricles in relaxting, so the pressure in the ventricles drops very low.

The pressure in the atria is higher than in the ventricles, so blood flows into the ventricles

39
Q

What happens in rheumatic heart disease?

A

AV valves aren’t closing fully during ventricular contraction

Blood flowing back into the atria

Turbulent flow, engendering a heart murmur

40
Q

What are heart sounds due to?

What are they?

A

Closure of valves

Sound 1: AV valves closing
Sound 2: Semilunar valves closing

41
Q

Does blood flow cause heart sounds?

A

Laminar flow (ie normal blood flow) does not bring about heart sounds

Turbulent flow through a leaky valve will bring about a murmur

42
Q

At which point in the ECG will the AV valves close?

A

QRS complex

ie ventricular contraction

43
Q

At which point during the ECG will semilunar valves close?

A

T wave

44
Q

What things does the Wigger’s diagram show us?

A 
1/ ECG
2/ Pressure in:
• aorta
• left ventricle
• left atrium
3/ Heart sounds
4/ Left ventricular volume

BIOM20002 - HSF (60 decks)

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