Lecture 16: CV Biophysics Flashcards

1
Q

What does the phrenic nerve innervate?

A

The diaphragm (C3, C4, C5)

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2
Q

What are the functions of the circulatory system?

A
  1. Transporting nutrients to tissues
  2. Transporting waste products away from tissues
  3. Transporting hormones for signaling
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3
Q

What is the measurement of volume?

A

Liters; ml

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4
Q

What is the measurement of velocity?

A

Units of distance/time (e.g., m/s; km/hour)

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5
Q

What is the measurement of pressure?

A

Force (e.g., mm Hg)

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6
Q

What is the measurement of area?

A

Size (e.g., cross-sectional area; surface area)

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7
Q

How is blood flow measured?

A

Volume/time (e.g., ml/min; l/min; ml/sec)

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8
Q

relate vascular resistance and blood flow

A

Less resistance = greater blood flow (& vice versa)

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9
Q

What does taking a measurement of blood pressure between the source of flow and resistance indicate?

A

A high blood pressure

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10
Q

What does taking a measurement of blood pressure after a source of resistance indicate?

A

A lower blood pressure (than if it were in between the heart and the source of resistance)

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11
Q

What drives blood flow?

A

Pressure

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12
Q

What drives brain blood flow and how is it altered?

A

CPP drives brain blood flow and is altered by vascular resistance

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13
Q

What is vascular conductance?

A

How ‘easy’ it is to drive blood flow through some conduit; the inverse of vascular resistance

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14
Q

Differentiate high vascular conductance and low vascular conductance.

A

High vascular conductance = easier to drive blood through a blood vessel
Low vascular conductance = more difficult to drive blood through a blood vessel

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15
Q

What does Poiseuille’s law relate?

A

Blood flow, pressure, and vascular resistance into a physics equation

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16
Q

Where is the majority of blood stored in the body?

A

Systemic veins (84%)

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17
Q

What does adequate cardiac output depend on?

A

If the veins can bring the blood back to the heart

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18
Q

How does the kidney control overall body volume?

A

It depends on how much blood we have; if the kidney retains more fluid, it increases blood volume (usually to make up for a deficit)

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19
Q

What is the total resistance in a system arranged in series?

A

R total = R1 + R2 + R3…

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20
Q

What is the total resistance in a system arranged in parallel?

A

1/Rtotal = 1/R1 + 1/R2 + 1/R3…
overall the resistance is lower in a system in parallel

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21
Q

What does the internal diameter of a vessel represent?

A

The cross-sectional area

cross sectional area = π x diameter

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22
Q

What happens if the cross-sectional area is a small number?

A

The blood flow through will be fast (high velocity)

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23
Q

What happens as the distance away from the heart increases in terms of cross-sectional area?

A

Cross-sectional area increases (e.g., capillaries 2500 cm²)

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24
Q

What happens to blood flow velocity as the distance away from the heart increases?

A

Blood flow velocity decreases

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25
Q

Contrast the aorta and capillaries in terms of blood flow velocity and cross-sectional area.

A

The aorta has a low cross-sectional area (2.5 cm²) with a high blood flow velocity (low resistance). The capillaries have a total cross-sectional area (2500 cm²) that is much larger than the aorta, thus creating a much slower blood flow velocity.

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26
Q

What is the formula for velocity of blood flow?

A

Velocity of blood flow = blood flow/cross-sectional area

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27
Q

Categorize the following vessels from highest resistance to lowest resistance: large arteries, arterioles, small arteries, aorta.

A
  1. Arterioles
  2. Small arteries
  3. Large arteries
  4. Aorta
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28
Q

What is the blood pressure measured on the proximal side of a high-resistance vessel?

A

High blood pressure

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29
Q

What is the blood pressure measured on the distal side of a high-resistance vessel?

A

Low blood pressure

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30
Q

What are the main resistance vessels that determine blood pressure?

A

Small arteries & arterioles

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31
Q

What is the blood pressure reading in the capillaries, veins, and right atrium?

A

10 mmHg

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32
Q

What is the blood pressure reading in the left atrium?

A

1-5 mmHg

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33
Q

What dictates blood flow through any tissue?

A

Metabolic rate

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34
Q

What does a high metabolic rate in a tissue indicate?

A

Low blood pressure (vessels are open) & therefore, we need to expand our blood volume (kidney may retain water to increase blood volume)

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35
Q

What is ideal blood flow?

A

Laminar Flow

Blood closer to the walls of the vessel meets more resistance; the middle of the blood flow projects faster through the tube due to less wall resistance

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36
Q

What are the characteristics of turbulent flow?

A

Disorderly; inefficient; blood is pushed into walls of blood vessels causing vasculature remodeling over time.

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37
Q

What can turbulent blood flow cause to aggregate and deposit onto vessel walls?

A
  1. Cholesterol
  2. Ca2+ (calcification)

two C’s

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38
Q

What does Reynolds’ equation measure?

A

The probability that turbulent flow will occur in a vessel

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39
Q

What percentage of cardiac output do the kidneys receive?

A

about 20% (or 1 LPM)

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40
Q

Why do kidneys require a high blood flow from the heart?

A

To be an efficient filter and function properly; the kidneys only partially rely on tissue metabolism for their blood flow.

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41
Q

What is Ohm’s law?

A

Voltage (mV) = current x resistance
V=IR

42
Q

What is Ohm’s law in the cardiovascular system?

A

∆P = blood flow (F) x vascular resistance (R)

43
Q

What is the rearranged formula for flow?

A

F = ∆P/R

44
Q

How does vessel diameter affect blood flow?

A

A small change in diameter creates a large change in blood flow.

45
Q

What is the rearranged formula for resistance?

A

R = ∆P/F

46
Q

How do you calculate renal vascular resistance?

A

R = ∆P/F
1. CO = 5LPM; Kidney = 1LPM or 1000 ml/min
2. Flow = volume/time = ml/min
3. R = (100 mmHg - 0 mmHg)/(1000 ml/min)
4. R = (0.1 mmHg)/(ml/min)

47
Q

What is the formula for vascular conductance?

A

Conductance = 1/resistance (the inverse of resistance)

48
Q

What does high conductance indicate?

A

Resistance is low

49
Q

describe laminar blood flow

A

ideal blood flow; normally the blood flow closest to the vessel walls meet a higher resistance, which projects the middle vessel blood to propel forward faster

50
Q

an area of BP measurement after a high vascular resistance area

“the one exception”

A

CVP

51
Q

most blood pressure measurements are measured _____ to high vascular resistance

distal or proximal

A

proximal

52
Q

the decrease in pressure as blood flows from the heart to smaller vessels is caused by:

A

high vascular resistance

53
Q

as resistance (R) increases, flow (F):

A

decreases

54
Q

as change in pressure (delta P) increases, flow (F)

A

increases

55
Q

blood flow through capillaries are primarily controlled by

A

arterioles

56
Q

what makes arterioles able to efficiently control blood flow through capillaries?

A

smooth muscle cells (densley packed within arterioles); these vsmc’s are able to constrict/dilate arterioles

57
Q

500-700 sq meters refers to

A

total surface area of all individual capillaries within the body

58
Q

the primary area where nutrient exchange/waste product collection happens in the circulatory system

A

capillaries

59
Q

metabolic rate tightly controls:

A
  1. nutrient delivery to tissue
  2. gas exchange (picking up CO2 & offloading O2)
60
Q

area of a circle

A

π(r2) = A
or
π x diameter = A

2r = d

61
Q

relate the aorta to the following terms: internal diameter, total cross-sectional area, and velocity

A

the internal diameter of ONE aorta is small, which would mean the total-cross sectional area would also be small, which would mean that there is a very high blood flow velocity

62
Q

relate the vena cavae to the following terms: internal diameter, total cross-sectional area, aorta, and velocity

A
  • TWO vena cavae
  • slightly larger internal diameter than aorta
  • ~4x larger total cross-sectional area than aorta
  • larger cross-sectional area means much slower blood flow velocity
63
Q

which vessels have the largest wall thickness to internal diameter ratio?

A

arterioles

64
Q

relate arterioles and wall thickness

A

arterioles have a very large wall thickness: internal diameter ratio

their wall thickness of arterioles regulates SVR + blood flow

65
Q

which vessels have the thinnest wall thickness

A

capillaries - they cell walls that are 1-cell layer thick

66
Q

capillary cell walls are made up of

A

ONE LAYER of endothelial cells
* endothelial cells are also found in veins, arteries, and inner layer of heart chambers

67
Q

these vessels are not effected by signaling peptides (i.e. norepi) to contract/relax

A

capillaries
* these vessels do NOT have vascular smooth muscle cells and therefore cannot contract/relax in response to norepi
* having no vsmc’s is also beneficial for capillaries so that there is less clutter for nutrient exchange

68
Q

relate capillary wall thickness to nutrient exchange

A

since the capillaries have very thin vessel walls, nutrients/gasses can easily exchange through these vessels

69
Q

rank the following vessels from highest blood flow velocity to lowest blood flow velocity: vena cavae, aorta, capillaries, arterioles

A
  1. aorta
  2. vena cavae
  3. arterioles
  4. capillaries
70
Q

rank the following vessels from highest total cross-sectional area to lowest lowest cross-sectional area : vena cavae, aorta, capillaries, arterioles

A
  1. capillaries
  2. arterioles
  3. vena cavae
  4. aorta
71
Q

the larger the cross-sectional area, the ____ the blood flow velocity

A

slower

ex) capillaries tcsa = 4500 cm2; slowest BF velocity

72
Q

arteriolar end of capillary, AKA:

A

arterial end

73
Q

delta P of capillary =

A

20 mmHg

74
Q

capillary arterial end pressure =

AKA arteriolar end pressure

A

30 mmHg

75
Q

capillary venous end pressure =

A

10 mmHg

76
Q

reabsorption occurs on this end of the capillary

A

venous end

77
Q

filtration occurs on this end of the capillary

A

arterial end

78
Q

name the 4 capillary starling forces

A
  1. Pcap
  2. Pisf
  3. πcap
  4. πisf
79
Q

hydrostatic* pressure inside the capillaries

*or hydraulic or physical fluid pressure

A

Pcap = 30 mmHg (arterial end); = 10 mmHg (venous end)
* pressure within the capillary

80
Q

hydrostatic pressure in the ISF

fluid outside all the capillaries & cells

A

Pisf = -3 mmHg

  • if the pressure is high enough & A POSITIVE PRESSURE, it can either: a.) oppose/reduce filtration at the arterial end or b.) promote reabsorption at the venule end
  • this pressure normally favors filtration & reversed with a “+” value of 3
81
Q

capillary colloid osmotic pressure/oncotic pressure

AKA plasma oncotic pressure

A

πcap = *28 mmHg
* IF the person is healthy and has enough albumin, fibrinogen, and enough immunoglobulins
* this pressure is due to the colloids dissolved in the blood
* this pressure keeps fluid inside the CV system (inside the capillaries)

82
Q

ISF colloid osmotic pressure

A

πisf = 8 mmHg

this pressure favors movement from the capillary to the ISF

83
Q

why is Pisf a negative number?

A

typically lymphatics pull excess fluid out of the interstitium

84
Q

things that would lower πcap (4)

A
  • hemorrhage
  • liver failure
  • sepsis
  • capillary walls become permeable to proteins
85
Q

what proteins lie outside of the capillary?

A
  • collagen
  • proteoglycan filaments
  • hyaluronic acid

these are large proteins

86
Q

contrast the amount of plasma colloid proteins vs ISF colloid proteins

A

plasma colloid proteins > ISF colloid proteins

87
Q

things that might increase πisf

A
  • trauma/damage to capillaries
  • crush injury
  • bacterial/viral infection
88
Q

what happens to proteins that leak out of the capillary and are stuck in the ISF?

A
  1. edema/swelling occurs
  2. lymphatic system tries to get rid of them (but happens very slowly) – the lymphatic system is not primarily specialized to get rid of proteins, but rather, fluid removal from ISF
89
Q

what is Kf

A

capillary filtration coefficient, which is primarily dealing with fluid, surface area, and relates these factors to how permeable the capillaries are to fluid

ex) if capillaries expand > more surface area > more movement

90
Q

3 main proteins that make up the capillary oncotic pressure

A
  1. albumin
  2. globulins
  3. fibrinogen (factor I)

28 mmHg

91
Q

what drives venous return as well as the lymphatic system?

A

skeletal muscle movement & contraction

the skeletal muscles squeeze against veins and the lymphatics that drive fluid through their one-way valves to return back to the CV system

92
Q

where does lymph fluid get returned to CV system?

A

lymphatic ducts at the top of the thorax

93
Q

lymphatic flow increases with:

A

movement
(increases up to 20 fold)

94
Q

in systemic circulation, this is the average capillary pressure

A

17.3 mmHg

  • this is due to capillaries getting larger from one end to the other
95
Q

the average NFP on any individual capillary

A

0.3 mmHg

96
Q

NFP = ?

A

Pcap - Pisf - πcap + π isf

97
Q

what is one area where NaCl is difficult to cross capillary membrane?

A

BBB

98
Q

as molecule size increases, capillary permeability:

A

decreases

ex) water vs albumin

99
Q

the glomerular capillary pressure

A

60 mmHg

  • this is 2x that of an average capillary pressure (30 mmHg) due to glomerular capillaries having a lot of filtration occuring here
100
Q

total of all glomerular capillaries filtration rate:

A

125 ml/min

101
Q

what does not get filtered our of glomerular capillaries?

A

RBCs
large proteins
large compounds