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FM1020 > PHYSIOLOGY - Cardiac Cycle > Flashcards

PHYSIOLOGY - Cardiac Cycle Flashcards

1
Q

What % of total ventricular volume flows into ventricles before atrial contraction?

A

Between 80-100%

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2
Q

What % of ventricular volume is pushed into ventricles by atrial contraction?

A

Up to 20%

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3
Q

What is diastesis?

A

Slow filling of ventricles - before atrial contraction

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4
Q

Under a slow heart rate, ventricular filling is complete at diastesis t/f?

A

True

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5
Q

What is tachycardia?

A

Increased heart rate

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6
Q

What happens to ventricular filling during tachycardia?

A
  • diastesis is shortened
  • contributions of atrial contraction to ventricular filling is increased
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7
Q

What is syncope?

A

Fainting

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8
Q

What can happen if inadequate ventricular filling occurs?

A

Fainting/syncope

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9
Q

What happens to significance of atrial contraction during intense exercise and why?

A

-atrial contraction becomes more significant
- because ventricular contraction can occur during rapid filling stage

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10
Q

In the atrial pressure curve, what does the A wave indicate?

A

The rise in pressure caused by atrial contraction

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11
Q

In the atrial pressure curve, what does the C wave indicate?

A

The increase in pressure in the atrium due to AV valves bulging into atria during ventricular systole

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12
Q

In the atrial pressure curve, what causes the V wave?

A

The rise in pressure associated with atrial filling

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13
Q

When does rapid filling of ventricles occur and what causes it?

A
  • occurs during ventricular diastole
  • Atrial pressure > Ventricular pressure since blood has been filling up the atria
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14
Q

During the A wave, what does the pressure increase by in the left atrium?

A

7-8mmHg

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15
Q

During the A wave what does atrial pressure increase by in the right atrium

A

4-6mmHg

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16
Q

What causes the venous pulse?

A
  • there are no valves at the junction of the veins and atria
  • pressure changes in atria are transmitted back to large veins
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17
Q

What is a significant venous pulse in the body?

A

Jugular venous pulse

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18
Q

What are the 3 waves of the venous pulse curve and what causes them?

A

A, C, V waves
- A by atrial contraction
- C by ventricular contraction
- V by volume in atria increasing

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19
Q

What is atrial fibrillation?

A

An arrythmia which causes uncoordinated contractions of atrial fibres.

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20
Q

What is absent from the ECG in atrial fibrillation?

A

The P wave

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21
Q

What are the irregular fluctuations on the ECG during atrial fibrillation called?

A

F waves

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22
Q

What is the range of time of the interval between ventricular contractions?

A

Between 0.35 and 0.95 seconds

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23
Q

What is the normal amount of time for the interval between ventricular contractions?

A

0.8 seconds

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24
Q

Why is atrial fibrillation not life threatening, in theory?

A
  • ventricular filling is normally almost complete during diastesis.
  • normal stroke volume, despite atrial contraction not occurring
  • electrical impulse can still be propagated in ventricles through AV node, provided it is the atrial fibres that are damaged and not the SA node
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25
Why can atrial fibrillation be dangerous?
Blood clots can form in the atria
26
What is the diastolic b.p of the aorta? (just before ventricles contract)
80mmHg
27
What is systolic b.p of aorta?
120mmHg
28
What causes the incisura/dicrotic notch on the aortic pressure curve?
There is a small amount of backflow of blood into the ventricles before the valves close (backflow needed to close valves)
29
How is high pressure maintained in the walls of the aorta, even in diastole?
The walls of the aorta are elastic.
30
Why does the pressure of the aorta decrease slowly during diastole?
The elastic recoil of the aorta pushes blood into peripheral arteries
31
What causes S1?
- The backflow of blood against the AV valves during systole, causing them to close. - the turbulent blood
32
What is the longest heart sound?
S1
33
What is the loudest heart sound?
S1
34
What stops the AV valves from flipping up into the atria?
Chordae tendinae
35
How long does S1 last?
0.14 seconds
36
What causes S2?
- upon diastole, the semilunar valves close. - reverberation of blood around the aortic walls
37
How long does S2 last?
0.11 seconds
38
When comparing an ECG and a phonocardiogram, when does S1 happen with respect to the ECG?
Just after QRS complex
39
When comparing an ECG to a phonocardiogram, when does S2 happen with respect to the ECG?
Just after the T wave
40
What is auscultation?
Listening to heart sounds with a stethoscope
41
Is the sound of the aortic valve or pulmonic valve louder in a normal heart?
Aortic valve
42
When someone has pulmonary hypertension, is the sound of the aortic valve or the pulmonic valve louder?
Pulmonic
43
Where is the auscultation point for the pulmonary valve?
Medial end of 2nd right intercostal space
44
Where is the auscultation point for the aorta?
Medial end of 2nd left intercostal space
45
Where is the auscultation point for the tricuspid valve?
5th left intercostal space, just lateral to sternum
46
Where is the auscultation point for the mitral valve?
Over apex of heart. 5th left intercostal space, midclavicular line
47
How can 2 extra heart sounds be heard?
Using electronical amplification of the sounds
48
What causes S3?
Blood rushing into left ventricle from atria during middle 1/3 of diastole
49
Is S3 or S4 louder?
S3
50
What kind of a sound is S3
A low rumbling sound
51
When is S3 considered abnormal ?
When someone is over 40 years old
52
What causes S4?
Inflow of blood intro ventricles following atrial contraction
53
What is an aortic stenosis?
The hole where the aortic valve is located gets smaller
54
What can aortic stenosis do to the phonocardiogram?
It makes S1 very loud and longer
55
What can aortic regurgitation do to the phonocardiogram?
Causes S2 to be longer and louder.
56
What point on the pressure-volume loop corresponds to pre load?
Point C
57
What point on the left ventricle pressure-volume loop represents ESV?
F
58
What is preload?
The tension on the left ventricle when it begins to contract
59
What causes preload?
The magnitude of EDV and end diastolic pressure
60
What point on the pressure-volume loop shows preload?
Point C
61
What is afterload?
The force against which the muscle is acting
62
What causes afterload?
The blood pressure in the aorta which the ventricle must exceeed to open the semilunar valves.
63
What could affect the afterload?
Changes in b.p
64
What point on the pressure-volume loop corresponds to the afterload?
Point D
65
What is contractility?
The strength of contraction at a given preload and afterload
66
What is another word for contractility ?
Ionotrophy
67
What can increase contractility?
Drugs e.g adrenaline
68
What can decrease contractility ?
Cardiac failure
69
What is an index of contractility ?
Maximum dP/dt —> maximum slope of ventricular pressure curve
70
At what volume will the diastolic pressure increase rapidly and why?
- At greater than 150ml - because the fibrous pericardium of the heart cannot fill further
71
What is the Frank-Starling law?
The systolic pressure increases linearly with EDV
72
What happens to systolic pressure at large EDVs?
Systolic pressure decreases because the actin and myosin filaments are stretched too far to contract properly.
73
What is stroke work output?
The physical work done by the ventricle to eject the stroke volume
74
What is volume pressure work?
Stroke work output
75
What is external work ?
Stroke work output
76
How can you calculate the External work value?
Find the area of the diastolic/systolic pressure-volume loop.
77
What happens to the EW value when the heart pumps larger quantities of blood?
Area of the loop becomes bigger, value of EW increase.
78
What happens to EW during cardiac failure?
EW will reduce in value.
79
What is ‘re-entry’? What is it’s effect?
- ‘Re-entry’ is when the cardiac muscle cells become excitable again (repolarised) i.e refractory period is shortened - this means that the same impulse can cause a second wave of depolarisation - leads to abnormal patterns of cardiac contraction
80
What can cause re-entry?
- increased tissue mass - decreased rate of conduction - shortened refractory period in response to certain drugs
81
What can cause a decreased rate of conduction?
- blockage of Purkinje system - ischaemia of the muscle - high blood potassium levels
82
What is fibrillation?
Abnormal cardiac rhythms caused by re-entry which ignore the pace setting effects of the SA node.
83
What is the most serious cardiac arrythmia?
Ventricular fibrillation
84
How long does it take for ventricular fibrillation to be fatal?
1-3 minutes
85
What does a defibrillator do?
Sends a high voltage alternating electrical current through the ventricles
86
How does a defibrillator work?
Stops fibrillation by simultaneously putting all myocardial cells in a refractory state. - this allows autorythmic cells to regain control

FM1020 (11 decks)

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