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CVS > Control Of Cardiac Output > Flashcards

Control Of Cardiac Output Flashcards

1
Q

What is total peripheral resistance?

A

The resistance to blood flow caused by all the systemic vasculature

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2
Q

What is afterload?

A

The load the heart must eject blood against (roughly equivalent to aortic pressure)

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3
Q

What is preload?

A

The amount the ventricles are stretched in diastole

Is related to EDV or central venous pressure

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4
Q

What is the pressure of the RA?

A

0-4mmHg

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5
Q

Pressure RV

A

25/4

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6
Q

Pressure of PA

A

25/10 mmHg

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7
Q

pressure LA

A

8-10mmHg

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8
Q

Pressure LV

A

120/10 mmHg

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9
Q

Pressure Aorta

A

120/80mmHg

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10
Q

What is compliance?

A

The amount the ventricle walls stretch increases with pressure- can be increased or decreasd in disease states

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11
Q

What is frank starlings law?

A

The higher the venous pressure the more the heart fills

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12
Q

What is the intrinsic control mechanism?

A

The more the heart pumps out means that the higher the pressure blood it will recieve into the RV which will stretch more so keeping up with the LV

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13
Q

What is typical stroke volume of a 70kg man?

A

70 ml

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14
Q

How much of the EDV is the stroke volume?

A

67%

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15
Q

CO=?

A

SV*HR

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16
Q

SV=?

A

EDV-ESV

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17
Q

What is blood a mixture of? What does it behave like?

A

A mixture of cells and plasma but behaves like a fluid

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18
Q

Why does blood slow down at the peripheries?

A

It is colder so is more viscous

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19
Q

What is turbulent flow?

A

Blood flows in all directions and continually mixes

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20
Q

When does turbulent flow occur?

A 
Rate of blood flow becomes too great
Blood passes by an obstruction
Blood makes a sharp turn
Blood passes over a rough surface
Increased resistance to blood flow
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21
Q

What is laminar flow? What is special about the way the blood flows?

A

Each layer of blood remains the same distance from the wall- the centre is the fastest as there is the least resistance so there is a parabolic curve

22
Q

How does the descending aorta pressure change with time?

A 
Systolic uptake- rapid rise
Peak systolic pressure
Systolic decline
Dicrotic notch- caused by elastic recoil of aorta
End diastolic pressure
23
Q

Pulse pressure=?

A

Peak systolic pressure- end diastolic pressure

Commonly 120-80= 40mmHg

24
Q

How can mean arterial pressure be estimated?

Below what value is organ perfusion impaired?

A

Diastolic pressure+ 1/3 pulse pressure.

If MAP falls below 70 then organ perfusion is impaired

25
Q

What is retrograde flow?

A

Blood in arteries flows backwards briefly during diastole and is greatest when TPR is high

26
Q

What is the pulse?

A

A shockwave that arrives slightly before the blood itself

27
Q

What is strength of the pulse determined by?

A

Force of ejection from LV
Therefore reduced pulse strength results from LV failure, aortic valve stenosis, hypovolaemia

Pulse pressure

28
Q

What is a weak pulse often described as?

A

Thready

29
Q

What effect does bradycardia have on pulse pressure?

A

Increases time in diastole so end diastolic pressure is lower so pulse pressure is greater

30
Q

What effect does a decreased peripheral resistance have on pulse pressure?

A

Pressure falls more rapidly so end diastolic volume is less so pulse pressure is larger

31
Q

What are the 7 stages of the cardiac cycle?

A 
Atrial systole
Isovolumetric contraction
Rapid ejection
Reduced ejection
Isovolumetric relaxation
Rapid filling
Reduced filling
32
Q

How much of the ventricular filling does atrial systole account for?

A

10%

33
Q

How is atrial systole represented on the ECG?

A

The p wave

34
Q

On the wiggers diagram which wave does atrial systole cause?

A

The a wave

35
Q

What happens after atrial systole?

A

AV valves close- this causes S1.

This closing causes a c wave in the atrial pressure curve

36
Q

What comes after atrial systole? What does this cause pressure wise?

A

Isovolumetric contraction

Causes a rapid rise in intraventricular pressure

37
Q

How is isovolumetric contraction represented on the ECG?

A

The QRS complex

38
Q

What happens after isovolumetric contraction?

A

Aortic/ PV open

39
Q

What happens after the aortic and pulmonary valves open?

A

Rapid ejection- rapid decrease in ventricular volume as blood is ejected into the aorta

40
Q

What effect does rapid ejection have on the atrial pressure on the WD?

A

D descent- atrial base is pulled downward as ventricle contracts

41
Q

What is happening as during rapid ejection?

A

Blood is flowing into atria from venous inputs

42
Q

What follows rapid ejection?

A

Reduced ejection- ventricles start to repolarise

43
Q

How is reduced ejection shown on the ECG?

A

The T wave

44
Q

What effect does repolarisation of the ventricles have on muscle tension?

A

Repolarisation leads to a decline in tension

45
Q

What is happening to atrial pressure during reduced ejection?

A

It is gradually rising due to continued return from venous supply
This creates the V wave on the WD

46
Q

How is the aortic valve made to close?

A

Ventricular pressure falls below aortic pressure which causes a brief backflow of blood
This makes the sound S2

47
Q

What phase follows reduced ejection

A

Isovolumetric relaxation- rapid decline in ventricular pressure but volume is constant as all valves are closed

48
Q

How is the dicrotic notch created ?

A

Is created during isovolumetric relaxation phase as aortic valve closes

49
Q

What happens to make the AV valves open? What effect does the opening of these have on atrial pressure?

A

IV pressure falls below atrial pressure so AV valves open which causes Y descent in atrial pressure

50
Q

What phase follows isovolumetric relaxation? What sign of pathology can sometimes be heard in this phase?

A

Rapid filling

S3 heart sound

51
Q

What is diastasis? Which phase of the cardiac cycle does this occur?

A

Reduced filling stage- Rate of filling slows down as the ventricle reaches its inherent relaxed volume- further filling is driven by venous pressure and atrial contraction

CVS (6 decks)

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