Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Cardiovascular System > Session 5 - Blood flow > Flashcards

Session 5 - Blood flow Flashcards

1
Q

Define velocity

A

-The rate of movement of fluid particles along a tube (distance/time)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

At a given flow, what is velocity inversely proportional to?

A

-Cross sectional area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

At a given flow, which vessels have high velocity?

A

-Those with a small cross-sectional area, eg aorta compared with high cross-secional area eg capillaries

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is lamina flow?

A
  • Flow of blood which has a gradient velocity from the middle to the edge of the vessels as
  • The fluid slides over one another in concentric layers as the velocity is highest in the centre and stationary at the edge
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is turbulent flow?

A

-Gradient velocity has broken down and the fluid tumbles over each other increasing resistance requiring a higher pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is a bruit?

A

-The noise which turbulent flow makes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What drives the flow of blood through BVs?

A

-The pressure gradient between the two ends of the vessel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What determines flow at a given pressure?

A

-Velocity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What determines velocity at a given pressure?

A
  • Viscosity of blood

- Radius of tube

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is viscosity?

A

-The extent to which the concentric layers of blood resist sliding over one another in laminar flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the relationship between velocity and viscosity?

A
  • Velocity is inversely proportional to viscosity, ie

- The higher the viscosity (the greater the resistance of the particles) the lower the average velocity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

-At a constant pressure, what is velocity proportional to?

A
  • Cross-sectional area

- Wider the tube, faster the flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

If pressure is fixed, increasing the cross-sectional area has what effect on velocity?

A

-Increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

If flow is fixed, increasing cross-sectional area has what effect on velocity?

A

-Decreases velocity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the equation to calculate flow?

A

-mean velocity x cross-sectional area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is resistance in a vessel determined by?

A
  • Viscosity of fluid

- Radius of vessel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the relationship between resistance and flow?

A
  • Flow is inversely proportional to resistance

- ie The higher the resistance the lower the flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is ohms law?

A

-Pressure= flow x resistance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How do changes in radius effect flow?

A

-Small changes in radius have a large effect on resistance and thus flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

If two vessels flow in series, how do you calculate the total resistance?

A

-Add the resistance of the tubes together?

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

-If vessels flow in parallel, what effect does this have on resistance?

A

-The total resistance is lower than any of the individual resistances

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What effect does pressure gradient have on flow?

A

-The higher the pressure gradient, the faster the flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

If flow is fixed, what effect does resistance have on the pressure gradient?

A

-The higher the resistance, the greater the pressure change from one end of the vessel to the other (ie the higher the pressure gradient)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

If pressure is fixed, what effect does resistance have on flow?

A

-The higher the resistance the lower the flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Is flow constant in the systemic circulation?

A

-Yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Why do arteries have a low pressure change?

A

-There is low resistance as the tube is relatively wide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Why is there a high pressure drop in arterioles?

A

-Resistance is high as the lumens narrow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

At a given flow, resistance is inversley proportional to cross-sectional area, so why do capillaries have a very low reistance?

A

-Because there are many connected in parallel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Why is the pressure drop low across the veins?

A

-There is low resistance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What effect does resistance of arterioles have on arterial pressure?

A

-The higher the resistance, the higher the arterial pressure

31
Q

What happens to arterial pressure, if CO increases but resistance remains the same?

A

-Arterial pressure will rise

32
Q

What causes turbulent flow?

A

-Increased resistance to flow

33
Q

What is transmural pressure?

A

-The pressure generated between the inside and outside of a vessel wall

34
Q

Because blood vessels are distensible, what effect does this have on resistance if the lumen widens?

A

-Drops

35
Q

How does distensibility of veins allow them to have capacitance?

A
  • When veins are collapsed there is no flow, as pressure increased the lumen widens and resistance decreases
  • As the vessel widens with increasing pressure, more blood transiently flows in than out -> thus they act as a store of blood
36
Q

Define systolic pressure

A

-The pressure of blood against the walls of the arteries when the ventricles are coontracting

37
Q

Define diastolic pressure

A

-The pressure of blood against the walls of the arteries when the ventricles are relaxing and refilling

38
Q

What is pulse pressure?

A

-The difference between the systolic and diastolic pressure (usually about 40mmHg at rest

39
Q

What is mean arterial pressure? How is it calculated?

A
  • The average arterial pressure across the cardiac cycle

- 2/3 diastolic + 1/3 systolic (heart spends 2/3 time in diastole and 1/3 systole)

40
Q

What is total peripheral resistance?

A

-The total resistance opposing blood flow in the systemic circulation

41
Q

What does arterial pressure need to be high enough to do?

A

-Drive the total CO through the total peripheral resistance

42
Q

-What effect does TPR have on arterial pressure?

A

-The higher the TPR, the higher the arterial pressure

43
Q

How does distensibility of arteries limit the pressure change between systole and diastole?

A

-The stretch of arteries allows more blood to flow into the arteries than out which limits pressure fluctuations as diastolic pressure does not drop as much

44
Q

Why is recoil of stretched arteries important?

A

-Allows the ‘stored’ blood to flow through the arterioles during diastole as the pressure is maintained by the recoil of the stretched arterial wall

45
Q

What determines the stroke volume?

A

-How hard the ventricles contract

46
Q

What is compliance of arteries, and how does it affect systolic pressure?

A

-Stectchiness of arteries -> the higher the degree of stretch, the more blood arteries can accommodate so bp does not rise as much during systole

47
Q

What is the link between age and compliance?

A

-With age, systolic pressure rises as vessels loose their stetchiness

48
Q

Why is diastolic pressure a better measure of TPR then systolic?

A

-Blood flows at a fixed rate during diastole as it is not effected by the stretch of arterial walls

49
Q

What determines diastolic pressure?

A
  • TRP

- Systolic pressure

50
Q

Define flow

A

-The volume of fluid passing a given point per unit time (vol/time)

51
Q

Draw the typical arterial waveform

A

-Waved line between systolic and diastolic pressure with a notch caused by closing of valve

52
Q

How do arterioles control distribution of flow?

A
  • Variable flow restriction by changing lumen diameter

- Pre-capillary sphincters

53
Q

What is meant by tonic contraction?

A

-Sustained contraction

54
Q

What controls skeletal muscle blood flow?

A

-Precapillary sphincters which rapidly open and close as needed

55
Q

Define vasoconstriction

A

-Redi=uciton in arterial diameter by contraction of smooth muscle in vessel walls -> increases resistance and reduces flow

56
Q

Define vasodilatation?

A

-Increase in arterial diameter by less contraction of smooth muscle in vessel walls -> decreased resistance and increased flow

57
Q

What is vasomotor tone?

A

-The continuous contraction of smooth muscle in BVs

58
Q

What controls vasomotor tone?

A

-NA release from sympathetic NS acting on a-1 receptors

59
Q

What antagonises vasomotor tone?

A

-Vasodilator metabolites

60
Q

How do vasodilator metabolites help to couple supply to demand

A

Increased metabolic activity -> increased vasodilator factors -> increased lumen-> decreased resistance-> increased blood flow -> decreased vasodilator as it is washed away -> vasoconstriction

Cycle starts again

61
Q

What determines the effect of vasodilator metabolites?

A

-The balance between the the rate at which they are produced and the rate at which bloodflow carries them away

62
Q

What is reactive hyperaemia?

A
  • Bloodflow to organ/limb temporarily prevented
  • Metabolising tissues still producing vasodilator factors
  • Accumulation as there is no flow
  • Arterioles dilate maximally
  • When perfusion is resotred, blood flow is very high as resistance is very low -> high blood flow needed for tissue demand
  • High blood flow washes away metabolites and smooth muscle contracts to normal
63
Q

What does autoregulation do?

A

-Ensures each organ only receives the supply it needs provided that supply pressure stays within limits

64
Q

What is autoregulation?

A

Supply pressure changes without a change in metabolic demand-> change in blood flow-> change in concentration of metabolites-> altered resistance of arterioles to match supply pressure -> bloodflow returns to appropriate level for metabolising tissue

65
Q

Why is TPR inversely proportional to the bodys need for blood?

A
  • All the tissues of the body alter the resistance of their own vessels in order to make bloodflow match metabolism
  • Thus the TPR is high if the bodys demand for blood is low
66
Q

What is central venous pressure?

A

-Pressure in the great veins supplying the heart

67
Q

What is venous return?

A

-The rate of blood flow back to the heart

68
Q

What determines the pressure in the veins?

A

-The volume of blood they contain, ie their capacitance

69
Q

What determines capacitance?

A

-The rate at which blood flows into and leaves the veins

70
Q

What controls the filling of the heart during diastole?

A

-Central venous pressure

71
Q

What determines CVP?

A
  • Return of blood from the body
  • CO of the heart
  • Gravity and muscle pumping
72
Q

What is muscle pumping?

A

-As muscles contract they compress the veins and drive the blood back to the heart

73
Q

How are superficial veins effected by gravity more than deep veins?

A
  • Deep veins are surrounded by fluid which is also effected by gravity to an equal extent so transmural pressure stays the same
  • Superficial veins are surrounded on one side by air which is less effected by gravity causing an increased transmural pressure resulting in swelling and pooling
74
Q

If blood pools in the legs, what effect does this have on CVP?

A

-Decreases it

Cardiovascular System (19 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions