Chapter 2: Physiology and Hemodynamics Flashcards Preview

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Flashcards in Chapter 2: Physiology and Hemodynamics Deck (109):
1

each heart beat pumps about _____mLs of blood into the aorta

70

2

Cardiac Contraction stages:

pressure in lt ventricle rises
lt ventricle pressure exceeds aortic pressure
aortic valve opens
blood is ejected
BP rises

3

Increased heart rate delivers _____ blood volume

increased

4

The heart pump:

generates pressure to move the blood
results in pressure wave (energy wave) that travels through the system

5

blood flow through system

lt ventricle
aorta
large arteries
arterioles
capillaries
venules
large veins
vena cava
rt atrium

6

the pumping action of the heart results in

high volume of blood in arteries to maintain high pressure gradient between arteries and veins

7

cardiac output governs

the amount of blood that enters the arterial system

8

what determines the amount of blood that leaves the arterial system

arterial pressure and total peripheral resistance

9

pressure is greatest at

the heart
gradually decreases as blood moves further away
this pressure difference is necessary to maintain blood flood

10

movement of any fluid between two points requires two things:

a pathway along which the fluid can move
difference in energy levels (pressure difference/energy gradient)

11

the amount of flow depends on

energy difference
resistance opposing movement

12

lower resistance = _____ flow rate

higher

13

Higher resistance = ____ flow rate

lower

14

the total energy contained in moving fluid is the sum of

pressure (potential), kinetic and gravitational energy

15

Pressure

potential/stored energy
major form of energy for circulation of blood

16

pressure is expressed in

mmHg

17

Kinetic energy

velocity
small for circulating blood

18

kinetic energy is expressed in

fluid density and velocity measurements

19

gravitational energy

equivalent to weight of column of blood extending from the heart to the level where pressure is measured
hydrostatic pressure (HP)

20

supine patient hydrostatic pressure

arteries and veins are at the same level as the heart
0mmHg against arteries and veins at ankle

21

standing patient hydrostatic pressure

at ankle pressure is about 100mmHg

22

a _____ is needed to move blood from one point to another

energy gradient

23

the greater the energy gradient the ____ the flow

greater

24

Inertia

tendency of fluid to resist chanegs in its velocity

25

as blood moves farther out to the periphery

energy is dissipated in the form of heat

26

energy is continually restored by the

pumping action of the heart

27

movement of fluid is dependent upon

physical properties of the fluid and
what is moving through

28

Resistance = 8 nl/r4pi

R= resistance
n= viscosity of blood
l= length of the blood vessel
r^4= radius of blood vessel

29

Resistance is directly proportional to

viscosity and length

30

Resistance is inversely proportional to

radius of blood vessel

31

what has the most dramatic effect on resistance?

a change in vessel diameter

32

Internal friction within a fluid is measure by

it's viscosity

33

Friction causes loss how

energy is lost in form of heat as rbcs rub together

34

elevated hematocrit _____ viscosity

increases

35

anemia ____ viscosity

decreases

36

Diminishing vessel size

increases frictional forces and heat energy loss

37

increase viscosity = _______ velocity

decreased

38

decrease viscosity = ____ velocity

increased

39

plug flow is seen at

vessel orgin

40

parabolic flow is usually seen

downstream

41

viscous energy loss is due to

increased friction between layer of blood

42

intertial losses occur

with deviations from laminar flow due to change in direction of velocity

43

what happens to the blood when deviations from laminar flow occur

parabolic flow profile becomes flattened
flow becomes disorganized

44

inertial energy loss typically occurs at

exit of a stenosis

45

Posieuille's equation defines

relationship between pressure, volume flow, resistance

46

Poiseuille's law helps answer the question

how much fluid moves through a vessel

47

Poiseuille's equation:

Q = P / R

Q= volume flow
P= Pressure
R= resistance

48

Poiseuille's equation and the relationship between contributors to flow itself

Q = (p1 - p2) pie r^4 / 8nL

Q= volume flow
P1 - P2 = pressures at proximal / dst ends
R = Radius of vessel
L = Length of vessel
n = viscosity of fluid

49

Radius of the vessel is

directly proportional to volume flow

50

the Law of Conservation of Mass explains what relationship

the relationship between velocity and area

51

Law of Conservation of Mass equation

Q = A x V

52

If area increases

velocity decreases

53

if area decreases

velocity increases

54

Bernoulli describes:

pressure and velocity relationship

55

The total energy contained in a moving fluid is the sum of

pressure, kinetic and gravitational energies

56

If there is a change in either kinetic, gravitational or pressure energies what happens

the other make up for the difference in order to maintain the original total fluid energy amount

57

if velocity increases, pressure

decreases

58

if velocity decreases, pressure

increases

59

pressure gradients are also known as

flow seperations

60

flow separation occur because

geometry change with or without intra-luminal disease, curves

61

in a flow separation velocity _____ and pressure ____

decreases
increases

62

flow separations result in regions of

stagnant flow or little movement

63

examples of flow separations include

bypass graft anastamosis site, valve cusp site

64

Reynolds Number (Re)

determines when fluid becomes unstable / disturbed

65

at which Reynolds number does laminar flow become turbulent

> 2000

66

Steady flow originates from

steady driving pressure, predictable behavior

67

in steady flow energy losses mainly occur from

viscous loss, can be described by poiseuille's equation

68

pulsatile flow

changes in both driving pressure condition as as well as response to the system

69

Systole

forward flow throughout the periphery (fluid acceleration)

70

late systole/ early diastole

temporary flow reversal

71

late systole/early disatole is caused by

phase shifted negative pressure gradient and peripheral resistance

72

late systole/early diastole causes

reflection of the wave proximally

73

the dicrotic nothc is related to

closure of the aortic valve and influence of peripheral resistance

74

Late diastole

flow is foward again
relective wave hits proximal resistance of the oncoming next wave and reverses

75

low resistance flow

flow is continuous (steady) feeling a dilated vascular bed

76

examples of low resistance flow

ICA, vertbral, renal, celiac, splenic, hepatic

77

high resistance flow

pulsatile in nature

78

what happens in high resistance flow

between pulses, hydraulic reflections travel back up vessel from the periphery producing flow reversals

79

examples of high resistance flow vessels

ECA
subclavian
aorta
iliac
extremity arteries
fasting sma

80

the reversal of flow in a high resistance vessel may disappear distal to a stenosis because

of decreased peripheral resistance, secondary to ischemia

81

doppler flow distal to a significant stenosis

lower resistance
more rounded in appearance
weaker in strength

82

what happens to a normally high resistant signal as it approaches a significant stenosis

normally biphasic or triphasic signal may become monophasic

83

doppler flow proximal to a significant stenosis is

higher resistant
could have no/minimal diastole

84

during vasoconstriction, pulsatile changes in medium/small sized arteries of the limbs are

increased and pulsatility changes in minute arteries are decreased

85

during vasodilation, pulsatile changes in medium/small sized arteries of the limbs are

decreased, lower resistant,
pulsatility changes are increased in minute arteries

86

as the inflow pressure falls as a result of stenosis, what does the periphery do?

vasodilate to maintain flow

87

at rest, total blood flow may be normal even in the presence of a stenosis/occluision.. why is this

development of a collateral network
compensatory decrease in peripheral resistance

88

Arterial obstruction can cause changes in collateral channels near the site of obstruction, these changes include:

increased flow
reversed flow direction
increased velocity
waveform pulsatility changes

89

location of collaterals can help provide information about what

location of stenosis or obstruction

90

exercise should induce:

vasofilation

91

vasodilation does what?

lowers distal peripheral resistance, increases blood flow

92

what also influences vasoconstriction and vasodilation of blood vessels

sympathetic innervation fibers which help regulate body temperature

93

what is the best single vasodilator of resistance vessels within skeletal muscles?

exercise

94

autoregulation

ability of most vascular beds to maintain a constant level of blood flow over a wide range of perfusion pressures

95

autoregulation is not present when

perfusion pressure drops below a critical level

96

BP rise:

constriction of resistance vessels

97

BP fall:

dilation of resistance vessels

98

exercise usually decreases what in the exercising extremity

decreases reflection, decreases resistance

99

what waveform is seen in extremity arteries after exercise

low resistant, monophasic caused by vasodilation

100

with proximal arterial obstructions what happens to the flow patterns distally

monophasic wave form due to peripheral dilatation

101

higher resistance signals may be seen when

vasoconstrction at the arteriolar level or distal arterial obstruction

102

flow to cool extremity

pulsatile

103

flow to warm extremity

continuous steady signal

104

a cross sectional area reduction of 75% = ____ diameter reduction

50%

105

effects of flow abnormality produced by a stenosis depends on 4 factors

length, diameter, shape of narrowing
multiple obstructions (resistances are additive)
obstructions in parallel vessels
pressure gradient (peripheral resistance beyond stenosis)

106

Proximal to a stenosis

flow is dampened

107

at the stenosis entrance

increase in doppler shift frequencies
spectral broadening
elevated velocities

108

flow disturbance in a stenosis occurs

due to interrupted flow stability with high velocity and eddies currents

109

at the exit of a stenosis

flow reversals
flor separations
eddy currents
spectral broadening