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Flashcards in deck_623225 Deck (60):
1

What does the pumping action of the heart tend to do to vesicular volume?

Remove blood from viens, pumps blood to arteries

2

What does a decrease in cardiac output tend to do to vesicular pressure

Increase venous pressure, decrease arterial pressure

3

If total peripheral resistance falls, what will happens to vesicular pressure at a constant cardiac output?

Arterial pressure will fall, venous pressure will rise

4

If total TPR rises, what happens to vesicular pressure if cardiac output constant?

Arterial pressure will rise, venous pressure will fall

5

What is TPR inversely proportional to?

The body's need for blood

6

What is the effect of metabolic changes on CVS, such as eating a meal?

TPR will change and generate signals in the form of changes in arterial and venous pressure

7

What is demand led pumping?

If the body needs more blood, the heart needs to pump more to meet the demand. This is expressed as changes in arterial and venous pressure

8

What is cardiac output?

Stroke volume x heart rate

9

Define stroke volume

The difference between end diastolic volume and end systolic volume. Amount of blood ejected at each heart beat

10

What is end diastolic volume determined by?

The filling of the heart, as during diastole the ventricles fill as venous pressure drives blood into them

11

What is end systolic volume?

The volume of blood in the left ventricle at the end of systole

12

What is end disastolic volume?

The volume of blood in the left ventricle at the end of diastole (filling)

13

To what pressure do the ventricles fill in diastole?

Until intraventricular pressure matches venous pressure `

14

What is the relationship between venous pressure and heart filling?

High the venous pressure, the more the hear fills in diastole

15

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

Ventricular compliance curve

16

Why will TPR resistance change if metabolism changes?

Due to vasodilator metabolites produced proportionally

17

What are the three factors which determine how much the ventricles fill during diastole?

1) Venous pressure2) Heart rate3) Total peripheral resistance

18

What is starlings law?

The more the heart fills, the harder it contracts (up to a limit).There harder it contracts, the bigger the stroke volume

19

Define pre load

The end diastolic stretch of the myocardion, determined by venous pressure

20

Define after load

Fore necessary to expel blood into the arteries - determines what happens during systole

21

What does a rise in venous pressure lead to?

A rise in stroke volume, due to increased ventricular filling

22

What does the yellow slope on this graph indicate

INSERT GRAPH Contractility of the ventricle

23

What does the red circled point indicate?

The critical value - No further expansion possible as muscle can stretch no further, due to squashing/damage, Ventricles are at full capacity

24

Define contractility

The ability of the cardiac muscle fiber to shorten, causing muscle contraction in response to an electrical impulse

25

What does the green line indicate?

Sympathetic activity, causing an increase in contractility

26

What is the term for the effect noradrenaline and adrenaline have on the heart, and what does it do?

Positive inotropic effectIncrrease stroke volume at a given pre-loa and after-load

27

What is force of contraction determined by?

End diastolic volume Contractility

28

What are the two things which determine how much ventricle empties depend on?

How hard the ventricles contractHow hard it is to eject blood

29

How can difficulty of blood ejection be modified?

Depends mainly on TPR - The harder it is to ject blood, the higher the pressure rises in the arteries

30

What factor does after-load determine?

The effect of a given force of contraction during systole

31

What happens to systolic volume and stroke volume if arterial pressure falls?

End systolic volume falls and stroke volume rises

32

What happens to stroke volume if venus pressure rises?

Stroke volume will rise

33

What are baroreceptors?

Stretch receptors located in carotid sinus and aorta which sense arterial pressure and determine autonomic outflow to the heart

34

Where do baroreceptors send signals?

To the medulla oblongata

35

What happens if a baroreceptor detects a fall in arterial pressure

Increase heart rateIncrease contractility

36

How would a baroreceptor increase heart rate?

By reducing parasympathetic activityBy increasing sympathetic activity

37

How would a baroreceptor increase contractility?

By increasing sympathetic activity

38

What is the bainbridge reflex?

Sensed in right atrium - A rise in venous pressure causes a rise in heart rate, via reduced parasympathetic activity

39

Describe in general terms the role of the medulla of the brain in CVS reflexes

A collection of neurones which modify cardiac behabiour and circulation via the ANS

40

How does the medulla oblangata change heart rate and contractility?

Heart rate - Alters the firing of the SAN to change heart rateContractilty - Uses sympathetic nervous system

41

What does a rise in venous pressure cause?

Increase stroke volumeIncrease heart rateIncreased cardiac output

42

If arterial pressure falls, what happens to blood flow resistance in certain tissues?

The resistance to blood flow through certain vascular beds such as the skin and gut will rise

43

What happens to venous capacitance if arterial pressure falls?

Venous capacitance will be reduced by veno-constriction

44

What are the consequences of an increase in heart rate?

Cardiac output risesSubsequent decrease in venous pressure Reduced diastolic filling due to reduced venous pressureReduced stroke volume

45

What happens to TPR if you are eating a meal?

Increased activity of gut leads to local vasodilationReduce TPR

46

What does reduced gut TPR during a meal lead to?

Rise in venous pressure - increased COFall in arterial pressure - Rise in hr, so COVenous pressure reduced by extra pumping of heart, and arterial pressure raised

47

What happens in circulatory system in exercise?

Massively increased demand for bloodMuscle pumping forces extra blood back to the heart

48

Why can't exercise produce response in same way as gastric?

Becase speed and scale of changes in venous pressure tend to overload the CVSHuge increase in venous pressure, massive decrease in arterial

49

Why is the huge increase in venous pressure during exercise dangerous?

Tends to overfill the heart and pushes the ventricles onto the overloaded section of the starling curve. Risk of pulmonary oedema because the outputs of the right and left ventricle cannot be matched.

50

What does the starling curve provide?

Matching stroke volume to right and left side of heart

51

How does pulmonary oedema come about as a result of overfilled heart during exercise?

Left heart cannot respond to right due to increased venous return, so blood accumulates in the lungs. Water forced out, causing decreased lung function via oedema.

52

How is overfilling of the ventricles prevented in exercise?

Increase in heart rate, which occurs as exercise begins. When venous pressure starts to rise, heart rate already high.

53

What effect does standing up have on the CVS?

Blood pools in the superficial veins of the legs because of gravity, causing fall in central venous pressure

54

What are the consequences of standing up and the subsequent decrease in central venous pressure

Central venous pressure falls, so cardiac output falls.Subsequent decrease in arterial pressureFall detected by baroreceptors, triggering rise in heart rate.

55

What are the three results of of a fall in arterial pressure detected by baroceptors on standing?

Rise in heart rateVaso constriction of skin and gut to increase TPRVeno constriction to drive blood to heart

56

What condition do older people develop which accentuates effects on blood pressure when standing up?

Postural hypotension

57

What is the direct effect of haemorrhage?

Decreased venous pressure, causing fall in cardiac output

58

What does the fall in cardiac output after haemorrhage due to decreased venous pressure cause?

Arterial blood pressure to fall, which is detected by baroreceptors.Heart rate increases, as does TPR.

59

What does the rise in heart rate and TPR as a result of haemorrhage cause to happen?

Further lower venous pressure - Rise of heart rate pumps blood out, TPR helps arterial pressure but lowers venous.Thus, veno constriction must take place.

60

Describe the effects of a long term increase in blood volume

* Kidney controls blood volume * If blood volume increases for days > venous pressure increases * Increased cardiac output * Increased arterial pressure (hypertrophy of smooth muscle) * Increased TPR * Increased arterial pressure (new set value) * Hypertension (treatment: diuretic/vasodilator)