Lecture 16: CV Biophysics Flashcards
1
Q
What does the phrenic nerve innervate?
A
The diaphragm (C3, C4, C5)
2
Q
What are the functions of the circulatory system?
A
- Transporting nutrients to tissues
- Transporting waste products away from tissues
- Transporting hormones for signaling
3
Q
What is the measurement of volume?
A
Liters; ml
4
Q
What is the measurement of velocity?
A
Units of distance/time (e.g., m/s; km/hour)
5
Q
What is the measurement of pressure?
A
Force (e.g., mm Hg)
6
Q
What is the measurement of area?
A
Size (e.g., cross-sectional area; surface area)
7
Q
How is blood flow measured?
A
Volume/time (e.g., ml/min; l/min; ml/sec)
8
Q
relate vascular resistance and blood flow
A
Less resistance = greater blood flow (& vice versa)
9
Q
What does taking a measurement of blood pressure between the source of flow and resistance indicate?
A
A high blood pressure
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)
11
Q
What drives blood flow?
A
Pressure
12
Q
What drives brain blood flow and how is it altered?
A
CPP drives brain blood flow and is altered by vascular resistance
13
Q
What is vascular conductance?
A
How ‘easy’ it is to drive blood flow through some conduit; the inverse of vascular resistance
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
15
Q
What does Poiseuille’s law relate?
A
Blood flow, pressure, and vascular resistance into a physics equation
16
Q
Where is the majority of blood stored in the body?
A
Systemic veins (84%)
17
Q
What does adequate cardiac output depend on?
A
If the veins can bring the blood back to the heart
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)
19
Q
What is the total resistance in a system arranged in series?
A
R total = R1 + R2 + R3…
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
21
Q
What does the internal diameter of a vessel represent?
A
The cross-sectional area
cross sectional area = π x diameter
22
Q
What happens if the cross-sectional area is a small number?
A
The blood flow through will be fast (high velocity)
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)
24
Q
What happens to blood flow velocity as the distance away from the heart increases?
A
Blood flow velocity decreases
25
Contrast the aorta and capillaries in terms of blood flow velocity and cross-sectional area.
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.
26
What is the formula for velocity of blood flow?
Velocity of blood flow = blood flow/cross-sectional area
27
Categorize the following vessels from highest resistance to lowest resistance: large arteries, arterioles, small arteries, aorta.
1. Arterioles
2. Small arteries
3. Large arteries
4. Aorta
28
What is the blood pressure measured on the proximal side of a high-resistance vessel?
High blood pressure
29
What is the blood pressure measured on the distal side of a high-resistance vessel?
Low blood pressure
30
What are the main resistance vessels that determine blood pressure?
Small arteries & arterioles
31
What is the blood pressure reading in the capillaries, veins, and right atrium?
10 mmHg
32
What is the blood pressure reading in the left atrium?
1-5 mmHg
33
What dictates blood flow through any tissue?
Metabolic rate
34
What does a high metabolic rate in a tissue indicate?
Low blood pressure (vessels are open) & therefore, we need to expand our blood volume (kidney may retain water to increase blood volume)
35
What is ideal blood flow?
**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
36
What are the characteristics of turbulent flow?
Disorderly; inefficient; blood is pushed into walls of blood vessels causing vasculature remodeling over time.
37
What can turbulent blood flow cause to aggregate and deposit onto vessel walls?
1. Cholesterol
2. Ca2+ (calcification)
| two C's
38
What does Reynolds' equation measure?
The probability that turbulent flow will occur in a vessel
39
What percentage of cardiac output do the kidneys receive?
about 20% (or 1 LPM)
40
Why do kidneys require a high blood flow from the heart?
To be an efficient filter and function properly; the kidneys only partially rely on tissue metabolism for their blood flow.
41
What is Ohm's law?
Voltage (mV) = current x resistance
V=IR
42
What is Ohm's law in the cardiovascular system?
∆P = blood flow (F) x vascular resistance (R)
43
What is the rearranged formula for flow?
F = ∆P/R
44
How does vessel diameter affect blood flow?
A small change in diameter creates a large change in blood flow.
45
What is the rearranged formula for resistance?
R = ∆P/F
46
How do you calculate renal vascular resistance?
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
What is the formula for vascular conductance?
Conductance = 1/resistance (the inverse of resistance)
48
What does high conductance indicate?
Resistance is low
49
describe laminar blood flow
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
an area of BP measurement **after** a high vascular resistance area
| "the one exception"
CVP
51
most blood pressure measurements are measured _____ to high vascular resistance
| distal or proximal
proximal
52
the decrease in pressure as blood flows from the heart to smaller vessels is caused by:
high vascular resistance
53
as resistance (R) increases, flow (F):
decreases
54
as change in pressure (delta P) increases, flow (F)
increases
55
blood flow through capillaries are primarily controlled by
arterioles
56
what makes arterioles able to efficiently control blood flow through capillaries?
smooth muscle cells (densley packed within arterioles); these vsmc's are able to constrict/dilate arterioles
57
500-700 sq meters refers to
total surface area of all individual capillaries within the body
58
the primary area where nutrient exchange/waste product collection happens in the circulatory system
capillaries
59
metabolic rate tightly controls:
1. nutrient delivery to tissue
2. gas exchange (picking up CO2 & offloading O2)
60
area of a circle
π(r2) = A
or
π x diameter = A
| 2r = d
61
relate the aorta to the following terms: internal diameter, total cross-sectional area, and velocity
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
relate the vena cavae to the following terms: internal diameter, total cross-sectional area, aorta, and velocity
* 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
which vessels have the largest wall thickness to internal diameter ratio?
arterioles
64
relate arterioles and wall thickness
arterioles have a very large wall thickness: internal diameter ratio
their wall thickness of arterioles regulates **SVR + blood flow**
65
which vessels have the thinnest wall thickness
capillaries - they cell walls that are 1-cell layer thick
66
capillary cell walls are made up of
ONE LAYER of endothelial cells
* *endothelial cells are also found in veins, arteries, and inner layer of heart chambers*
67
these vessels are not effected by signaling peptides (i.e. norepi) to contract/relax
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
relate capillary wall thickness to nutrient exchange
since the capillaries have very thin vessel walls, nutrients/gasses can easily exchange through these vessels
69
rank the following vessels from highest blood flow velocity to lowest blood flow velocity: vena cavae, aorta, capillaries, arterioles
1. aorta
2. vena cavae
3. arterioles
4. capillaries
70
rank the following vessels from highest total cross-sectional area to lowest lowest cross-sectional area : vena cavae, aorta, capillaries, arterioles
1. capillaries
2. arterioles
3. vena cavae
4. aorta
71
the larger the cross-sectional area, the ____ the blood flow velocity
slower
| ex) capillaries tcsa = 4500 cm2; slowest BF velocity
72
**arteriolar** end of capillary, AKA:
arterial end
73
delta P of capillary =
20 mmHg
74
capillary arterial end pressure =
| AKA arteriolar end pressure
30 mmHg
75
capillary venous end pressure =
10 mmHg
76
reabsorption occurs on this end of the capillary
venous end
77
filtration occurs on this end of the capillary
arterial end
78
name the 4 capillary starling forces
1. Pcap
2. Pisf
3. πcap
4. πisf
79
hydrostatic* pressure inside the capillaries
| *or hydraulic or physical fluid pressure
Pcap = 30 mmHg (arterial end); = 10 mmHg (venous end)
* pressure within the capillary
80
hydrostatic pressure in the ISF
| fluid outside all the capillaries & cells
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
capillary colloid osmotic pressure/oncotic pressure
| AKA plasma oncotic pressure
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
ISF colloid osmotic pressure
πisf = 8 mmHg
this pressure favors movement from the capillary to the ISF
83
why is Pisf a negative number?
typically lymphatics pull excess fluid out of the interstitium
84
things that would lower πcap (4)
* hemorrhage
* liver failure
* sepsis
* capillary walls become permeable to **proteins**
85
what proteins lie outside of the capillary?
* collagen
* proteoglycan filaments
* hyaluronic acid
| these are large proteins
86
contrast the amount of plasma colloid proteins vs ISF colloid proteins
plasma colloid proteins > ISF colloid proteins
87
things that might increase πisf
* trauma/damage to capillaries
* crush injury
* bacterial/viral infection
88
what happens to proteins that leak out of the capillary and are stuck in the ISF?
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
what is Kf
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
3 main proteins that make up the capillary oncotic pressure
1. albumin
2. globulins
3. fibrinogen (factor I)
| 28 mmHg
91
what drives venous return as well as the lymphatic system?
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
where does lymph fluid get returned to CV system?
lymphatic ducts at the top of the thorax
93
lymphatic flow increases with:
movement
(increases up to 20 fold)
94
in systemic circulation, this is the average capillary pressure
17.3 mmHg
* this is due to capillaries getting larger from one end to the other
95
the average NFP on any individual capillary
0.3 mmHg
96
NFP = ?
Pcap - Pisf - πcap + π isf
97
what is one area where NaCl is difficult to cross capillary membrane?
BBB
98
as molecule size increases, capillary permeability:
decreases
ex) water vs albumin
99
the glomerular capillary pressure
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
total of all glomerular capillaries filtration rate:
125 ml/min
101
what does not get filtered our of glomerular capillaries?
RBCs
large proteins
large compounds
