Systemic Circulation and Hemodynamics Flashcards
(120 cards)
1
Q
the volume of blood contained in the arteries is called what?
A
stressed volume-meaning the blood volume under high pressure
2
Q
which blood vessel type has the highest resistance to blood flow?
A
arterioles
3
Q
what is a special feature of the arterioles besides them having the highest resistance to blood flow?
A
they are also the site where resistance can be changed by alterations in sympathetic nerve activity
4
Q
what is the pressure/ volume like of veins?
A
low pressure; high volume
5
Q
the volume of the blood contained in the veins is called what?
A
unstressed volume- meaning the blood volume under low pressure
6
Q
where is the cross-sectional area the greatest?
A
in the capillaries
7
Q
where is the volume of blood the greatest?
A
in the veins
8
Q
what happens to the resistance and the flow as the diameter of the blood vessel changes?
A
as the diameter increases, the resistance is going to decrease and flow is going to increase; as the diameter decreases, the resistance is going to increase and flow is going to decrease
9
Q
what does Poiseuille’s law calculate?
A
resistance through a tube
10
Q
what happens to the resistance has viscosity goes down?
A
resistance decreases as viscosity decreases
11
Q
when would viscosity decrease?
A
in an anemic state
12
Q
what happens if there is increased hematocrit?
A
it will decrease the flow (because resistance is increased)
13
Q
how would you find the total resistance for vascular resistances that are in a series?
A
you simply add the individual resistances for the total
14
Q
how would you find total resistance for vascular resistance beds that are in parallel?
A
1/ Rtotal= the sum of the 1/R1…1/R2 etc.
15
Q
what does adding resistance beds in series do to the total resistance?
A
it increases the total resistance
16
Q
what does adding resistance beds in parallel do to the total resistance?
A
it decreases the total resistance
17
Q
how are capillaries arrange: series or parallel?
A
capillaries are arranged in parallel–> low resistance
18
Q
where is the site of the greatest control of blood flow and TPR?
A
the arterioles
19
Q
what does increased sympathetic stimulation cause in the blood vessels?
A
vasoconstriction
20
Q
what does vasoconstriction cause?
A
reduced flow, increased TPR or increased pressure
21
Q
what does decreased sympathetic stimulation cause?
A
vasodilation
22
Q
what does vasodilation cause?
A
increased flow, decreased TPR or decreased pressure
23
Q
what is velocity like in arteries? In capillaries?
A
high in arteries and low in capillaries
24
Q
what contributes to blood flow becoming turbulent?
A
when velocity is high, cross sectional area is large, or viscosity is low
25
what is reynold's number?
an equation which takes into account the velocity, cross sectional area, and viscosity to predict when turbulence will occur
26
when is it considered that there is a transition from laminar to turbulent flow?
when reynold's number is greater than 2000
27
what does turbulent blood flow lead to?
sound (bruits) and lesions (arteriosclerosis)
28
what is compliance (aka capacitance)?
the change in volume/ the change in pressure
29
what is compliance (aka capacitance) the reciprocal of?
elastance
30
where is the highest compliance?
in the veins
31
where is the lowest compliance found?
in the arteries
32
which is more elastic, arteries or veins?
arteries
33
blood is being pushed forward not only through the pressure gradient but also through what?
the elastic recoil of the arteries
34
when is the elastic recoil of the arteries prominent?
during diastole
35
what affect does aging and atherosclerosis have on compliance and how?
they decrease compliance by reducing the amount an artery can distend during systole and by reducing the recoil during diastole
36
what is the effect of smooth muscle contraction in veins?
you are contracting the blood forward; redistributing blood to the arteries
37
what is the pulsatile nature of the aortic end of the pressure due to?
compliance and distention of the walls during ejection and recoil during relaxation
38
which blood vessel sees the largest pressure drop?
arterioles
39
what is the driving force for blood flow?
the pressure differences that exist between the heart and the blood vessels
40
what is pulse pressure?
the difference between systolic and diastolic pressure
41
if all other factors are equal, what does the magnitude of the pulse pressure reflect?
the blood ejected from the left ventricle in a single beat AKA STROKE VOLUME
42
how do you calculate the mean arterial pressure?
1/3( SBP) + 2/3 (DBP) (bc you spend a lot more time in diastole than you do in systole)
43
what is the normal mean arterial pressure?
93.3 mm Hg
44
a decrease in compliance would have what effect on the pulse pressure?
a decrease in compliance would cause pulse pressure to increase
45
what effect does arteriosclerosis have on pressure?
it increases SBP, MAP, and pulse pressure; DBP does not generally change
46
what effect does aortic stenosis have on pressure?
it decreases SBP, MAP, and pulse pressure; DBP does not generally change
47
what is the general rule of thumb for the venous system?
low pressure, high compliance, and large volume
48
what effect does venoconstriction have on the venous system?
it decreases venous "compliance" with minor changes to the radius of the veins (so there is little resistance change)
49
what is the backflow of blood in veins prevented by?
valves
50
what does venous pressure in the cardiac cycle look like?
there is an A wave, a C wave, and a V wave
51
when does the A wave occur?
during atrial contraction (so between the mid p-wave on the ECG and R wave of the QRS complex)
52
when does the C wave occur?
during ventricular contraction
53
what is the C wave caused by?
partially by slight backflow of blood into the atria at the onset of ventricular contraction but mainly by the bulging of the AV valves backwards into the atria due to increases in pressure in the ventricles
54
when does the V wave occur?
at the end of the ventricular contraction
55
what causes the V wave?
slow flow of blood into the atria from veins while the AV valves are closed
56
What are the walls of the arterioles rich with?
extensive smooth muscle
57
what is the composition of metarterioles?
they have more limited smooth muscle along the walls
58
what do the capillaries have that further control flow?
precapillary sphincters
59
in the capillary walls, what allow for the passage of water soluble substances such as glucose or electrolytes?
clefts
60
where are clefts found to be very small? Where are clefts found to be very large?
Very small in the brain (tight junctions) and very large in the liver and the gut
61
how do lipid soluble substances such as O2 and CO2 pass across the capillary walls?
through plasma membranes
62
how do larger molecules pass through the capillary walls?
through vesicles
63
Not all capillaries are open all the time; what is vasomotion?
it is the term used for the oscillating flow of blood through capillaries, which flows intermittently on and off every few seconds or minutes
64
how does vasomotion occur?
from the oscillating contraction of metarterioles and precapillary sphincters
65
what is vasomotion largely regulated by?
oxygen levels in the tissues; as oxygen consumption increases in the tissue, the frequency of vasomotion and duration the sphincters remain open increases to increase blood flow
66
what does the starling equation calculate?
the flow of water either out of a capillary or drawing into the capillary
67
what does a positive starling number indiccate?
that the flow of water is out of the capillary
68
what does a negative starling number indicate?
there is a drawing of water into the capillary
69
what represents fluid moving out of the capillary (+)?
filtration
70
what represents fluid moving into the capillary (-)?
absorption
71
what 2 forces act on the fluid exchange that is occurring in capillaries?
hydrostatic pressure and osmotic/oncotic pressure
72
what type of forces are the hydrostatic pressures?
pushing forces
73
what type of forces are the osmotic/oncotic forces?
pulling forces
74
what is the equation used for fluid exchange across the capillary walls?
```
J= [(Pcap-Pinterstial)- (Osmotic pressure cap.-osmotic pressure interstitial)}
J= flow
```
75
what is the general rule about the hydrostatic pressure at the arteriole side and what effect does this have?
it is usually higher on the capillary side; so therefore, you are more likely to see filtration (+)
76
what is the general rule about the hydrostatic pressure at the venous side?
it is lower, so you are more likely to see absorption (-)
77
what is the capillary osmotic pressure caused by?
plasma proteins that tend to draw fluid from the interstitial fluid into the blood
78
what is the interstitial fluid pressure?
the pressure to force fluid into the capillary from the interstitial fluid
79
what is the interstitial osmotic pressure?
tends to pull fluid from the capillary into the interstitial fluid
80
how do the lymphatics re-enter venous circulation?
at the subclavian vein
81
what effect does elevated venous pressure have on Pc? and when might you have this?
Pc can be increased by elevated venous pressure; this can occur during right-sided heart failure
82
when can Pi be altered?
by restricted lymphatic flow or increased driving force out of a capillary
83
when can osmotic pressure of the capillary be decreased?
by reduced levels of albumin (such as in starvation or liver failure)- causes fluid to stay in the interstitial space
84
when might interstitial osmotic pressure be altered?
by restricted lymph flow or inflammation
85
what is acute control of blood flow achieved by?
rapid changes in local vasodilation or vasoconstriction of arterioles, metarterioles, and precapillary sphincters
86
what is autoregulation?
the maintenance of a constant blood flow to an organ in the face of changing arterial pressure
87
what does the vasodilator theory state?
decreased oxygen availability increases the formation of vasodilator substances
88
what are the vasodilator substances?
adenosine, CO2, adenosine phosphate compounds, histamine, potassium, and hydrogen ions
89
what does the oxygen demand theory state?
as oxygen levels rise or decrease the contraction of precapillary sphincter smooth muscle constricts or relaxes
90
what is active hyperemia?
the concept that blood flow to an organ is proportional to its metabolic activity
91
what is reactive hyperemia?
an increase in blood flow in response to or reacting to a prior period of decreased blood flow
92
what is the most important mechanism for coronary circulation?
local metabolic control
93
what is the most important mechanism for cerebral circulation?
local metabolic control
94
what is the most important mechanism during exercise for skeletal muscle?
local metabolic control
95
what is the most important mechanism during rest for skeletal muscle?
sympathetic control
96
what is the most important mechanism for temperature regulation of the skin?
sympathetic control
97
what is the most important mechanism for pulmonary circulation?
local metabolic control
98
what is the most important mechanism for renal circulation?
local metabolic control
99
what NT causes vasocontriction?
norepinephrine and epinephrine (norepinephrine greater than epinephrine)
100
what effect does Angiotensin II have on blood vessels?
it acts as a vasoconstrictor
101
what effect does vasopressin have on the blood vessels?
vasoconstrictor
102
what effect does serotonin have on the blood vessels?
it acts as a vasoconstrictor
103
what are the two main vasodilators we discussed?
bradykinin and histamine
104
what ions are considered vasodilators?
K+, Mg2+, H+, acetate, and citrate, and CO2
105
what is coronary blood flow mostly regulated by?
local control mechanisms- largely under metabolic control
106
what is the rate and contractility of the heart controlled by?
the sympathetic nervous system
107
when does coronary blood flow begin and when does it end?
begins during ventricular repolarization and lasts into diastole
108
when is coronary blood flow partially occluded?
during systole
109
what is almost entirely controlling the cerebral blood flow?
metabolic control, Pco2, and H+
110
injury to the head can result in what?
vasodilation and edema
111
what are the critical pressures that affect cerebral blood flow?
150 mmHg and 50 mmHg
112
what is the mean artial pressure in the pulmonary circulation?
about 15 mmHg
113
at rest, what is the skeletal blood flow governed by?
central and baroreceptor control
114
how does skeletal muscle dilate during exercise?
through the release of local factors like ATP, adenosine, NO, K+, and lactate
115
what effect does the central command that occurs during exercise have on the blood vessels?
it will cause an increase in the sympathetic outflow- this causes constriction of vein and constriction of the splanchnic and renal arterioles
116
what effect do the local responses that occur during exercise have on the blood vessels?
it causes an increase in vasodilator metabolites- so there will be a dilation of skeletal muscle arterioles and there will be a decreased in TPR
117
what causes constriction of the blood vessels in the skin?
constriction is induced by the alpha-1 adrenergic receptors (sympathetics)
118
what happens to the central sympathetics in the skin as body temperature rises?
the central sympathetic activation are inhibited to induce vasodilation of arterioles
119
what does trauma to the skin cause release of?
histamine
120
what effect does histamine have in the skin?
it produces a triple response in skin: a red line, a red flare, and a wheal (local edema)
