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BMS10 > Intro to CVS & Physics of Blood Flow > Flashcards

Intro to CVS & Physics of Blood Flow Flashcards

1
Q

Give two features of the circulatory system of the body

A

Closed

Double pump

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2
Q

How would you describe the resistance and pressure in the pulmonary circulation generally?

A

Low

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3
Q

How would you describe the resistance and pressure in the systemic circulation generally?

A

High

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4
Q

How is the pulmonary circulation arranged?

A

In series with systemic

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5
Q

How is the systemic circulation arranged?

A

Largely in parallel

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6
Q

What is the mean arterial pressure in the pulmonary circulation?

A

16mmHg

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7
Q

What is the mean arterial pressure in the systemic circulation?

A

92mmHg

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8
Q

Describe the changes in pressures in the systemic circulation

A

Very high in left ventricle

High in large arteries

Main decrease occurs in arteries and arterioles

Relatively lower decrease through capillaries

Decreases in venules

Remains low in veins

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9
Q

How do the pressure changes in the pulmonary circulation compare to those of the systemic circulation?

A

Similar trend but at much lower pressures

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10
Q

What is cardiac output?

A

Volume of blood ejected from left ventricle per minute

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11
Q

What is the cardiac output of the average person?

A

~5L/min

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12
Q

How can you calculate cardiac output?

A

Stroke volume x heart rate

Mean arterial pressure / total peripheral resistance

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13
Q

What is the stroke volume of the average person?

A

70-80ml/beat

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14
Q

What is the heart rate of the average person?

A

60-75 bpm

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15
Q

What is the ejection fraction?

A

Amount of blood ejected compared to what remains (%)

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16
Q

What is the ejection fraction used for?

A

Evidence of heart failure (<40%)

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17
Q

What is the ejection fraction of the average healthy person?

A

60-70%

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18
Q

How do you calculate the ejection fraction?

A

Stroke volume / end diastolic volume

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19
Q

What is TPR?

A

Total peripheral resistance

Resistance to flow mostly due to small arteries and arterioles

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20
Q

Which side of the heart is affected by TPR?

A

Left

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21
Q

What is the informal term used to describe TPR?

A

Afterload

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22
Q

How can you calculate mean arterial blood pressure?

A

Diastolic pressure + pulse pressure/3

CO x TPR

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23
Q

How do you calculate pulse pressure?

A

Systolic pressure - diastolic pressure

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24
Q

What is systolic pressure?

A

The maximum pressure reached in the heart

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25
What is diastolic pressure?
The minimum pressure reached in the heart
26
For how long is the heart in systole?
1/3 of the time
27
What is venous return?
Blood flow into the heart
28
What is the venous return of the average person?
~5L/min
29
What determines the filling of the heart with blood?
Central venous pressure/preload
30
How do you calculate flow generally?
Pressure / resistance
31
What is normal blood pressure?
120/80mmHg
32
What is systole?
High pressure ejection of blood into large conduit arteries (lots of smooth muscle and elastin)
33
How many layers of smooth muscle are there in the large conduit arteries?
60-100
34
What happens to the large conduit arteries during systole and diastole?
Systole = stretch to store energy Diastole = no outward flow so stored energy used to maintain flow (recoil)
35
At what level must blood pressure always be measured?
At heart level
36
What is Darcy's law?
Flow = (P1 - P2) / R = pressure difference / resistance
37
What is Poiseuille's law?
R = 8VL / πr^4
38
What equation do you get when you combine Darcy's and Poiseuille's laws?
Flow = (P1 -P2).πr^4 / 8VL
39
What is the most important factor in determining resistance?
Radius of vessel/tube
40
How is the resistance to flow affected by a larger length?
Increased
41
How is the resistance to flow affected by a higher fluid viscosity?
Increased
42
How is the resistance to flow affected by vasoconstriction?
Increased
43
What are the assumptions made when using Poiseuille's law?
Incompressible fluid Newtonian fluid Laminar flow
44
How much thicker is blood than water?
3-4 times
45
How does an increase in red cell mass affect plasma viscosity?
Increased
46
How does anaemia affect plasma viscosity?
Decreased
47
Where is the fastest flow in a tube/vessel and why?
Centre Concentric layers of force due to viscous drag at sides of tube
48
What is axial streaming?
Cells aligning in fastest moving fluid
49
What is the Fahraeus-Lindqvist effect?
Describes how blood viscosity changes with vessel diameter (less blood cells in capillaries = lower viscosity)
50
What causes turbulent flow?
High velocity flow, sharp edges and branch points Disrupt laminar flow
51
What causes heart murmurs?
Turbulent flow High velocity blood flow due to stenosis/narrowed heart valves
52
What is Reynold's number for laminar flow?
<2300
53
What is Reynold's number for turbulent flow?
>4000
54
How does flow change as pressure increases in a rigid tube?
Flow increases proportionately
55
How does flow change as pressure increases in a distensible tube?
Flow increases proportionately then exponentially as tube dilates
56
How does flow change as pressure increases in a distensible tube with myogenic tone?
In response to pressure increase, smooth muscle contracts to limit flow
57
Why is high velocity flow not desirable in blood vessels?
Causes damage to walls
58
How do you calculate the total resistance in a series circuit?
Add resistances
59
How do you calculate the total resistance in a parallel circuit?
Add conductances to get reciprocal of total resistance
60
How are conductance and resistance related?
Conductance is the reciprocal of resistance
61
Is total resistance higher in a circuit in series or parallel?
Series
62
What is the advantage of having vascular beds arranged in parallel?
Resistance in one bed can be changed without greatly affecting net resistance or the resistances of other beds
63
If blood pressure is constant, what controls flow through a tissue?
The tissue's own resistance (ie. constriction/dilation of its own vessels)

BMS10 (13 decks)

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