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

Flashcards in Control of Cardiac Output Deck (67):
1

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

Arterial pressure will fall, Venous pressure will rise

2

Why will arterial pressure fall if total peripheral resistance falls?

Because the same volume into lower resistance allows pressure to fall

3

Why will venous pressure rise if total peripheral reistance falls?

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

4

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

Arterial pressure will rise
Venous pressure will fall

5

Why does arterial pressure fall if cardiac output falls?

Not as much volume is pumped around

6

Why does venous pressure rise if cardiac output falls?

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

7

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

TPR is inversely proportional to need

8

What can cause a change in total peripheral resistance?

Changes in metabolism

9

Why does metabolism change total peripheral resistance?

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

10

What is meant by demand led pumping?

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

11

How is demand expressed?

As changes in arterial and venous pressure

12

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

Falls in arterial pressure and rises in venous pressure

13

What is cardiac output the produce of?

Stroke volume 
Heart rate

14

How is cardiac output calculated?

CO = SV x HR

15

What affects stroke volume and heart rate?

Arterial and venous pressures

16

How is stroke volume calculated?

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

17

What is end diastolic volume?

The volume in ventricles after relaxed

18

What is the end systolic volume?

The volume in ventricles after contraction

19

Is end systolic volume minimum systolic volume?

Not under normal conditions

20

Is end diastolic volume maximum diastolic volume?

Not under normal conditions

21

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

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

22

What is the ventricle connected to during filling?

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

23

When do the ventricles fill until?

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

24

What does a higher venous pressure result in?

The heart fills more during diastole

25

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

The ventricular compliance curve

26

What happens if ventricular muscle is stretched before contracting?

It contracts harder

27

What is the ventricle contracting harder when stretched known as?

Starlings Law of the Heart

28

What does Starlings Law of the Heart state?

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

29

What limits the filling of the heart?

The pericardial sac

30

What does a harder contraction lead to?

A bigger stroke volume

31

What do rises in venous pressure automatically lead to?

Rises in stroke volume

32

What does the Starling curve relate?

Stroke volume to venous pressure

33

What is the slope of Starlings curve known as?

The contractility of the ventricle

34

What is contractility saying?

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

35

How is force of contraction different from contractility?

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

36

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

Inotropy

37

What does positive inotropy do?

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

38

What does how much the ventricle empties depend on?

How hard it contracts
How hard it is to eject blood

39

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

More comes out in systole

40

What happens if atrial pressure falls?

End systolic volume will fall, so stroke volume will rise

41

What is force of contraction determined by?

End diastolic volume 
Contractility

42

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

Due to Starlings Law of the Heart

43

What increases contractility?

Sympathetic activity

44

What is difficulty of ejecting blood known as?

Aortic impedance

45

What does aortic impedance depend on?

Mainly, total peripheral resistance

46

What is the result of increased aortic impedance?

The pressure rises in the artries

47

What is preload?

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

48

What is preload related to?

End diastolic pressure

49

What is preload increased in?

Hypervolemia 
Regurgitation of cardiac valves
Heart failure

50

What is afterload?

The resistance that the left ventricle must overcome to circulate blood

51

When is afterload increased?

Hypertension  Vasoconstriction

52

What does an increased afterload lead to?

An increased cardiac workload

53

What does heart rate need to control it?

A sensory system that’s not intrinsic

54

What is autonomic outflow to the heart controlled by?

Signals from baroreceptors

55

What senses arterial pressure?

The carotid sinus

56

Why can the carotid sinus sense arterial pressure?

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

57

Where does the carotid sinus send signals to?

The medulla

58

What happens if arterial pressure falls?

Heart rate and contractility are increased

59

How is heart rate increased?

Reducing parasympathetic activity 
Increasing symphathetic activity

60

How is contractility increased?

Increasing the sympathetic activity

61

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

Diastole time shortens

62

What is the problem with diastole time shortening?

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

63

What is given to slow down heart rate?

Beta blockers

64

What is the purpose of beta blockers?

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

65

Where is a rise in venous pressure sensed?

Right atrium

66

What does a rise in venous pressure lead to?

Reduced parasympathetic activity, and so a rise in heart rate

67

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

Bainbridge reflex