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ESA 2- Cardiovascular System > Control of Cardiac Output > Flashcards

Control of Cardiac Output Flashcards

1
Q

What happens to arterial and venous pressure if total peripheral resistance falls and cardiac output remains constant?

A

Arterial pressure will fall, Venous pressure will rise

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2
Q

Why will arterial pressure fall if total peripheral resistance falls?

A

Because the same volume into lower resistance allows pressure to fall

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3
Q

Why will venous pressure rise if total peripheral reistance falls?

A

Because there is more blood in the venous system than before, as we are not taking any more blood out of the system form the venous side, so in a snapshot of time, the rate that blood is going into the venous system increases

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4
Q

What happens to arterial and venous pressure if cardiac output rises and total peripheral resistance remains constant?

A

Arterial pressure will rise

Venous pressure will fall

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5
Q

Why does arterial pressure fall if cardiac output falls?

A

Not as much volume is pumped around

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6
Q

Why does venous pressure rise if cardiac output falls?

A

Because the blood stays in the venous system for longer, as less is pumped from the heart, and so the pressure rises

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7
Q

How are total peripheral resistance and the body’s need for blood related?

A

TPR is inversely proportional to need

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8
Q

What can cause a change in total peripheral resistance?

A

Changes in metabolism

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9
Q

Why does metabolism change total peripheral resistance?

A

It generates ‘signals’ in the form of changes in arterial and venous pressure. The pressure change is noticed by the body so it can change to respond

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10
Q

What is meant by demand led pumping?

A

If the body needs more blood, the heart needs to pump more to meet demand

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11
Q

How is demand expressed?

A

As changes in arterial and venous pressure

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12
Q

To what does the heart respond to by pumping more blood?

A

Falls in arterial pressure and rises in venous pressure

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13
Q

What is cardiac output the produce of?

A

Stroke volume

Heart rate

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14
Q

How is cardiac output calculated?

A

CO = SV x HR

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15
Q

What affects stroke volume and heart rate?

A

Arterial and venous pressures

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16
Q

How is stroke volume calculated?

A

It is the difference between end diastolic volume and end systolic volume

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17
Q

What is end diastolic volume?

A

The volume in ventricles after relaxed

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18
Q

What is the end systolic volume?

A

The volume in ventricles after contraction

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19
Q

Is end systolic volume minimum systolic volume?

A

Not under normal conditions

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20
Q

Is end diastolic volume maximum diastolic volume?

A

Not under normal conditions

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21
Q

Why are end systolic and diastolic volumes not at their maximum?

A

Otherwise the heart would have nowhere to go when responding to demands

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22
Q

What is the ventricle connected to during filling?

A

It is isolated from the arteries, and connected to the veins

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23
Q

When do the ventricles fill until?

A

Until the walls stretch enough to produce an intraventricular pressure equal to venous pressure

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24
Q

What does a higher venous pressure result in?

A

The heart fills more during diastole

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25
Q

What is the relationship between venous pressure and ventricular volume known as?

A

The ventricular compliance curve

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26
Q

What happens if ventricular muscle is stretched before contracting?

A

It contracts harder

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27
Q

What is the ventricle contracting harder when stretched known as?

A

Starlings Law of the Heart

28
Q

What does Starlings Law of the Heart state?

A

The more the heart fills, the harder it contracts, up to a limit

29
Q

What limits the filling of the heart?

A

The pericardial sac

30
Q

What does a harder contraction lead to?

A

A bigger stroke volume

31
Q

What do rises in venous pressure automatically lead to?

A

Rises in stroke volume

32
Q

What does the Starling curve relate?

A

Stroke volume to venous pressure

33
Q

What is the slope of Starlings curve known as?

A

The contractility of the ventricle

34
Q

What is contractility saying?

A

That for a given amount of stretch, if efficiency is increased, you get a higher stroke volume

35
Q

How is force of contraction different from contractility?

A

Force of contraction is one myocyte being pulled
Contractility is the efficacy of the whole heart
Force of contraction is variable within contractility

36
Q

What is an increase in efficiency known as in cardiac terms?

A

Inotropy

37
Q

What does positive inotropy do?

A

Increases the slope of the Starling curve, and therefore increases stroke volume

38
Q

What does how much the ventricle empties depend on?

A

How hard it contracts

How hard it is to eject blood

39
Q

What is the result of it being easier to eject blood?

A

More comes out in systole

40
Q

What happens if atrial pressure falls?

A

End systolic volume will fall, so stroke volume will rise

41
Q

What is force of contraction determined by?

A

End diastolic volume

Contractility

42
Q

Why is the force of contraction determined by end diastolic volume?

A

Due to Starlings Law of the Heart

43
Q

What increases contractility?

A

Sympathetic activity

44
Q

What is difficulty of ejecting blood known as?

A

Aortic impedance

45
Q

What does aortic impedance depend on?

A

Mainly, total peripheral resistance

46
Q

What is the result of increased aortic impedance?

A

The pressure rises in the artries

47
Q

What is preload?

A

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

48
Q

What is preload related to?

A

End diastolic pressure

49
Q

What is preload increased in?

A

Hypervolemia
Regurgitation of cardiac valves
Heart failure

50
Q

What is afterload?

A

The resistance that the left ventricle must overcome to circulate blood

51
Q

When is afterload increased?

A

Hypertension Vasoconstriction

52
Q

What does an increased afterload lead to?

A

An increased cardiac workload

53
Q

What does heart rate need to control it?

A

A sensory system that’s not intrinsic

54
Q

What is autonomic outflow to the heart controlled by?

A

Signals from baroreceptors

55
Q

What senses arterial pressure?

A

The carotid sinus

56
Q

Why can the carotid sinus sense arterial pressure?

A

It has a thinner wall, and so can bulge out or contract depending on pressures in the artery

57
Q

Where does the carotid sinus send signals to?

A

The medulla

58
Q

What happens if arterial pressure falls?

A

Heart rate and contractility are increased

59
Q

How is heart rate increased?

A

Reducing parasympathetic activity

Increasing symphathetic activity

60
Q

How is contractility increased?

A

Increasing the sympathetic activity

61
Q

What happens to diastole if there is an increased heart rate?

A

Diastole time shortens

62
Q

What is the problem with diastole time shortening?

A

There is less time to fill the chambers, which is counterproductive in the long term

63
Q

What is given to slow down heart rate?

A

Beta blockers

64
Q

What is the purpose of beta blockers?

A

To slow down the heart rate so there is more time for filling of the ventricles

65
Q

Where is a rise in venous pressure sensed?

A

Right atrium

66
Q

What does a rise in venous pressure lead to?

A

Reduced parasympathetic activity, and so a rise in heart rate

67
Q

What is the rise in venous pressure causing a rise in heart rate known as?

A

Bainbridge reflex

ESA 2- Cardiovascular System (18 decks)

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