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Spring '24 > Physics Exam #1 > Flashcards

Physics Exam #1 Flashcards

Only includes hemodynamics part one powerpoint, not part 2. Part 2 is in iPad.

1
Q

in terms of the circulatory system, this term describes cardiac function

A

pulsatility

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2
Q

in terms of the circulatory system, these 2 terms describe the composition of the blood

A

viscosity
density

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3
Q

in terms of the circulatory system, these 2 terms describe the vascular smooth muscle tone

A

elasticity
compliance

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4
Q

how many liters of blood does the circulatory system contain?

A

5 liters (4-8 liters)

normal range for cardiac output is 4-8 liters

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5
Q

how much water makes up plasma?

A

90%

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6
Q

In blood, these cells dominate.

A

RBC’s (red blood cells) or erythrocytes
40%

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7
Q

define hematocrit

A

percentage of erythrocytes in whole blood

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8
Q

what is the term meaning “the percentage of erythrocytes in whole blood”

A

hematocrit

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9
Q

these cells are larger than erythrocytes and less numerous

A

WBC’s (white blood cells)

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10
Q

these are smaller than erythrocytes

A

platelets

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11
Q

what shape are platelets and what do they do?

A

they are disc shaped
they help with coagulation

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12
Q

In relation to the ultrasound transducer, what do red blood cells do?

A

they reflect the US beam back to the transducer

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13
Q

a decrease or increase in the hematocrit DIRECTLY correlates to an increase or decrease in the

A

VISCOSITY (of blood)

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14
Q

what are the units of viscosity

A

poise

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15
Q

compare the viscosity of blood plasma to water (percentage)

A

viscosity of blood plasma is about 50% greater than that of water

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16
Q

specifically, “viscosity” has to do with what in relation to a “fluid in motion”?

A

resistance to flow

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17
Q

what layer of the artery is thicker and has elastic properties

A

tunica media

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18
Q

why do arteries have an abundance of elastic tissue and less smooth muscle?

A

to accommodate for the stress of high pressure

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19
Q

arteries are compliant TRUE OR FALSE

A

TRUE

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20
Q

what is compliance?

A

the ability of a hollow organ (vessel) to distend and increase volume with increasing pressure

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21
Q

an effect of pulsatile flow

A

the windkessel effect

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22
Q

what is the windkessel effect

A

when the pressure pulse forces a fluid into a COMPLIANT vessel such as the aorta, it expands and increases the volume within it….
will show as systolic flow

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23
Q

why can you feel your pulse on your neck or wrist?

A

windkessel effect

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24
Q

what’s the difference in blood characteristics between anemia and polycythemia

A

anemia leads to DECREASE in hematocrit & DECREASE in viscosity

polycythemia is an INCREASE in hematocrit & INCREASE in viscosity

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25
Q

to move more viscous fluid requires more

A

energy

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26
Q

in the circulatory system, energy is lost in the form of…. what rubs against each other…

A

heat
RBC’s rub against each other… think friction… heat

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27
Q

in regards to the windkessel effect, this event will show as systolic flow

A

when pressure pulse forces fluid into a compliant vessel (ex. aorta) it expands and increases the volume within it

***recoil is diastolic flow

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28
Q

veins expand in response to

A

increased transmural pressure

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29
Q

in terms of layers, how are the veins different than arteries

A

tunica intima - has single layer of endothelial cells
tunica media - thinner than artery, collagen fibers, smooth muscle

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30
Q

are veins more compliant than arteries? why or why not

A

yes, this is mainly due to their thinner walls (much more elastic too - veins are distensible and can hold large volumes of blood)
known as venous compliance

too compliant though is bad. Could be associated with edema

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31
Q

abnormally compliant veins can be associated with what pathology

A

edema

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32
Q

what component of the cardiovascular system is known as the “capacitive” component

A

venous system… “capacitive” because the venous system can store a large “capacity” of blood

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33
Q

what percentage of the body’s blood volume resides in the veins at rest?

A

65%

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34
Q

veins change shape; talk about it

A

since they’re elastic they can increase in diameter by an increase in intravascular pressure

they can also decrease diameter by an increase in surrounding tissue pressure.

during exercise the cross sectional shape of a vein changes from hourglass to oval to round

***large volume increase with a very small increase in pressure

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35
Q

when veins expand what decreases or goes down?

A

resistance to flow decreases!
(this INCREASES outflow toward the heart) - transmural pressure is high

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36
Q

veins empty rapidly and then return to

A

their typical semi-collapsed state

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37
Q

respiration has a profound effect on these 2 things…

A

venous pressure and flow

38
Q

respiration affects venous flow for 2 reasons:

A
  1. venous system is low pressure
  2. muscles responsible for respiration alter pressures in the thorax and the abdomen
39
Q

anatomically, breathing affects venous flow how (2 ways)

A
  1. venous flow in the legs
  2. venous return to the heart, which comprises venous flow from the head, arms, and flow from the IVC to the heart
40
Q

a vein at rest is in what kind of state

A

a semi-collapsed state… veins empty rapidly then return to rest!

41
Q

flow question as related to breathing: flow INCREASES from the abdominal cavity to the RA and DECREASES from the legs to the abdominal cavity during….

A

INSPIRATION (remember the sniff test, what happens exactly)

42
Q

flow question as related to breathing: the return of flow from the legs to the abdomen INCREASES and from the abdomen to the RA DECREASES during…

A

EXPIRATION

43
Q

during inspiration the chest cavity __________, diaphragm moves ________, and a __________ pressure is created in the chest.

A

expands, downward, negative

***negative pressure creates SUCTION that increases venous return to the heart - that’s why venous flow from the head, arms, and vena cava INCREASES during inspiration (more blood flow to head)

44
Q

but ALSO why is venous blood flow decreased in the legs during inspiration???

A

because during inspiration, the diaphragm also presses into the abdomen. Abdominal compression INCREASES abdominal pressure and DECREASES venous blood flow in the legs

45
Q

during expiration the diaphragm moves _______, pressure in the chest is ________. Increase thoracic pressure reduces __________.

A

upward, increased, venous return to the heart
(rib cage gets smaller as rib muscles relax and the diaphragm decompresses the abdomen - decreases abdominal pressure and increases venous blood flow in the legs)

***thus, venous flow from the head, arms, and the vena cava all DECREASE during expiration (less blood flow to head)

46
Q

Inspiration five main points

A

diaphragm moves downward toward the abdomen
thoracic pressure decreases
abdominal pressure increases
venous return to the heart increases
venous flow in legs decreases

47
Q

Expiration five main points

A

diaphragm moves upward into thorax
thoracic pressure increases
abdominal pressure decreases
venous return to the heart decreases
venous flow in legs increases

48
Q

when the calf muscle contracts

A

venous blood returns to the heart.

49
Q

what does the effectiveness of the calf muscle pump depend on (2)

A

depends on the forcefulness of the venous contraction and competence of venous valves

50
Q

how does the calf muscle pump work…

A

by shunting blood out of the deep system (veins, venules, capillaries)

51
Q

explain the calf muscle pump clinically beginning with “muscular contraction…”

A

“muscular contraction compresses the intramuscular veins and surrounding superficial veins, raising venous pressure and facilitating blood flow towards the heart.”

52
Q

as blood is moved OUT of the calf veins, these 2 pressures drop

A

intramural and transmural pressure drops

53
Q

what will happen if muscle contraction is weak in the calf muscle pump?

A

less blood is moved out the leg and transmural pressure will remain high — this is why edema occurs in sedentary patients (esp with bad venous valves)

54
Q

incompetent venous valves are dangerous because

A

faulty valves allow backward blood flow back down, pulled down by gravity. Blood will be coming into the leg via the arteries faster than it can exit the leg via the veins and then edema happens.

55
Q

with a normal efficient muscle pump we expect (3)

A

no flow during rest or low flow
augmented forward flow tip contraction (integrate)
no flow or low flow on relaxation

56
Q

with an INEFFICIENT muscle pump due to venous incompetence we expect (4)

A

reflux at rest (retrograde)
augmented flow on contraction
reflux on relaxation
the blood goes back up and then falls back down

57
Q

Fluid in our body cannot be destroyed, it can only be

A

CONVERTED by absorption or by being turned into heat

58
Q

the movement of any fluid medium between 2 points requires 2 things:

A

a route for fluid to flow (obviously)
a pressure gradient (difference in energy levels) between the two

59
Q

blood always follows the path of

A

least resistance

60
Q

total energy is the sum of these 3 energies:

A

potential (pressure) energy, kinetic (movement) energy, gravitational energy

pressure energy - created by heart
kinetic energy - energy in motion (mass and speed )
gravitational energy - hydrostatic energy

61
Q

you have two columns. one is way taller than the other. which one will have a higher hydrostatic pressure?

A

the taller one

62
Q

at the level of the heart, the hydrostatic pressure is

A

0 mmHg
“above” the heart we have a “negative” hydrostatic pressure or decreased pressure

“below” the heart we have a “positive” hydrostatic pressure or increased pressure

63
Q

what do we mean when we say “blood pressure?”

A

blood “pressure” is the hydrostatic “pressure” that is exerted by blood on the wall of a blood vessel

64
Q

blood pressure depends on (3)

A
  1. cardiac output
  2. vascular resistance
  3. total blood volume

blood pressure depends on #1 and #2

blood pressure = cardiac. output x resistance

65
Q

in THE SUPINE PATIENT, the hydrostatic pressure is what and why?

A

it is zero because all parts of the body are at the same level as the heart. A pressure reading on a supine patient is an accurate one; represents true circulatory pressure

66
Q

In terms of inertia… what is necessary for blood to flow (or any fluid) from one point to another?

A

a pressure gradient aka energy gradient

**high pressure to low pressure (old knowledge)

67
Q

define inertia

A

tendency of an object to resist any change in its motion

68
Q

as blood move out to the periphery what will it lose?

A

it will lose energy in the form of heat but the heart pump will keep the inertia

69
Q

3 types of energy loss (not really lost but converted; either absorbed or converted into heat)

A
  1. frictional
  2. viscous
  3. inertia
70
Q

5 things that cause energy loss

A
  1. rougher vessel surface
  2. sharper angles (ex. bends, kinks, twists, branching)
  3. higher “viscosity” blood aka higher “hematocrit”
  4. Higher volumetric flow
  5. increased velocity
71
Q

define frictional energy loss

A

every converted to heat from rubbing - blood flow energy loss mainly due to this one

72
Q

which has greater friction and resistance to flow… a smaller vessel or larger one

A

smaller vessel

73
Q

define viscous energy loss (5)

A

an increase in viscosity leads to an increase in energy loss
if a fluid is thick it moves freely
takes way more energy to move thicker fluid
increase viscosity = decreased velocity
decreased viscosity = increased velocity

74
Q

define inertial energy loss (4)

A

fluid resists changes in velocity
changes in speed lead to energy loss
increased or decreased speed - energy loss either way
as blood moves farther out to periphery, energy dissipates in form of heat

75
Q

what is the driving force behind fluid flow

A

pressure

76
Q

in terms of units, what is pressure

A

force per unit area

77
Q

equation for pressure is

A

force divided by area

78
Q

in a fluid that is not moving, how is pressure distributed?

A

EVENLY!!!
it is evenly distributed throughout a fluid that is not moving

79
Q

true or false… pressure exerts its force in ALL directions

A

true

80
Q

2 things can generate a pressure gradient in the body

A

the heart
gravity

81
Q

a pressure gradient in flow is similar to a pressure gradient in electricity where Voltage = current x resistance. In flow, the equation for a pressure gradient is

A

flow x resistance

82
Q

what does Ohm’s Law state?

A

Ohm’s law states that the current through a conductor between two points is directly proportional to the voltage across the two points

83
Q

electrical resistance is reported in units of ohms. In the circulatory system, the resistance vessels are called

A

arterioles

84
Q

define compliance

A

ability of a vessel to distend and increase volume with increasing pressure

85
Q

what propels blood along an artery?

A

the elastic recoil or ARTERIAL COMPLIANCE

86
Q

missed on exam in calf muscle pump, muscular contraction would lead to an _________ in venous pressure, whereas muscular relaxation would lead to a _________ in venous pressure

A

increase, decrease

87
Q

missed on exam capacitance is best described as

A

a measure of the ability to hold a change in volume per change in time

88
Q

missed on exam the inverse relationship between pressure and velocity is described as

A

Bernoullis equation

89
Q

missed on exam flow resistance depends most strongly on which of the following

A

flow radius

90
Q

missed on exam proximal to, at, and distal to a stenosis, WHAT must be constant?

A

volume flow rate

91
Q

missed on exam Poiseuille’s Law refers to the flow in a vessel and is determined by what three things?

A

Resistance, Viscosity, Pressure

Spring '24 (9 decks)

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