Exam 2 circulation Flashcards
(231 cards)
1
Q
What are the main functions of systemic circulation?
A
1) Deliver adequate oxygen and nutrients to systemic tissues
2) remove CO2 and other waste products from systemic tissues
2
Q
What serves as a conduit for transport of hormones, and other substances and allows these substances to
potentially act at a distant site from their production
A
Systemic circulation
3
Q
What are systemic arteries functional role in systemic circulatory system
A
Carry blood under high pressure out to the tissue beds
4
Q
What is the function of arterioles and precapillary sphincters in the circulatory system
A
Act as control valves to regulate local flow
5
Q
What is the function of capillaries that are one cell layer thick
A
Exchange between tissue(cells) and blood
6
Q
What is the function of venules in systemic circulation
A
Collect blood from capillaries
7
Q
What is the function of systemic veins
A
Return blood to heart/dynamic storage
8
Q
What is proportional to metabolic demand?
A
Blood flow
9
Q
What is controlled by local tissue flow
A
Cardiac output
10
Q
What control is independent of local flow or cardiac output
A
Arterial pressure
11
Q
What makes up the components of blood vessels
A
Endothelium, elastic tissue, smooth muscle, fibrous tissue
12
Q
What is the composition of the aorta, artery, vein, and capillary?
-Elastic tissue = (1)
– Smooth muscle =(2)
– Fibrous tissue = (3)
A
-Aorta = 1>3>2
-Artery= 2>1>3
-Vein 1=2=3
Capillary = endothelium only
13
Q
What 4 things make up hemodynamics
A
1) flow = F
2) pressure gradient = change in pressure
3) resistance (R)
4) Ohm’s law
14
Q
What is the equation for ohm’s law
A
V= IR (analogous to delta P = FR)
- V = voltage
- I = current flow
- R = resistance
15
Q
What is flow equal to?
A
F = velocity x cross sectional area
16
Q
T/F = at a given flow, the velocity is inversely proportional to the total cross sectional area
A
T
17
Q
T/F flow is directly proportional to delta P and inversely proportional to resistance (R)
A
True
F = change in pressure / R
18
Q
What is the driving force of blood
A
Pressure gradient
19
Q
Pressure gradient is proportional to what?
A
Proportional to flow (F)
20
Q
At a given F the greater the drop in P a segment or compartment the greater the ____ to flow
A
Resistance
21
Q
Where does the greatest resistance to flow occur?
A
Pre-capillary resistance vessels
22
Q
What are pre-capillary resistance vessels
A
Arterioles, met-arterioles, pre-capillary sphincters
23
Q
What do each of the abbreviations stand for in the resistance equation R= 8nl/ r4
A
- n = viscosity
- l = length of vessel
- r = radius
24
Q
In the parallel circuit what is the relationship of 1/Rt
A
1/Rt = 1/R1 + 1/R2 + 1/R3….
Rt< smallest individual R
25
What is the relationship of Rt in the series circuit?
```
Rt = R1+ R2+R3....Rn
Rt= sum of individual R’s
```
26
What is systemic circulation primarily made of
Parallel circuit
27
What are some advantages of parallel circuitry?
1) independence of local flow control
2) minimizes total peripheral resistance (TPR)
3) oxygen rich blood supply to every tissue
28
What is the total vascular resistance (TVR) equal to
TVR = the sum of total pulmonic resistance + total peripheral resistance
29
What is viscosity
The internal friction of a fluid associate with intermolecular attraction
30
What is most viscosity in the blood due to?
RBC’s
31
With blood what is viscosity’s relationship with velocity
Viscosity is inversely proportional to velocity
32
What is the viscosity of blood, plasma, and water
3, 1.5, 1
33
When velocity decreases why does viscosity increase?
elements in blood sticking together more
34
Where can cells get stuck and what effect does it have?
They can get stuck at constriction points and increases apparent viscosity
35
What does fibrinogen do?
Increases flexibility of RBC’s
36
What happens in small vessels with regards to viscosity
In small vessels cells line up which decrease viscosity and offsets the viscosity at constriction points to some degree
37
What is the normal range of hematocrit
38-45%
38
What is hematocrit primarily made up of
RBC’s
39
What are the characteristics of laminar flow
Streamline, silent, most efficient, normal
40
What makes up turbulent flow
Cross mixing, vibrational noise, least efficient, frequently associated with vessel disease (bruit)
41
What is reynold’s number
Probability statement for turbulent flow, the greater the R# the greater the probability for turbulence
42
What do the abbreviations for reynolds number stand for?
| V, D, p, n
- v = velocity
- D = tube diameter
- p = density
- n = viscosity
43
What does the R3 = if R#<2000, R#>3000
- if R#<2000 = laminar flow
| - if R#>3000 = turbulent flow
44
What is the purpose of a doppler ultrasonic flow-meter
Ultrasound to determine velocity of flow
45
How does a doppler ultrasonic flow-meter work
RBC’s move toward transmitter, compress sound waves, increase frequency of returning waves
46
Broad vs. narrow frequency bands
- broad band is associated with turbulent flow
| - narrow band is associated with laminar flow
47
What are the 2 things used for determination of cardiac output
- fick principal
| - indicator dilution
48
What can help determines vessel flow
- venous occlusion plesthymography (momentary limb blood flow)
- doppler ultrasonic flowmeter
- vascular flow cuffs
49
What is the fick principal
Measures blood flow to tissue/organ
50
What are the 3 port systems of the fick principal
- input blood concentration of x
- output blood concentration of substance x
- addition/removal of substance x from tissue
51
What is the fick principal equation
Flow= amount of substance per min / AV difference
52
PBF =
O2 uptake / AV O2 diff.
53
What is the indicator dilution based on
Conservation of mass
54
Distensibility vs. compliance
- distensibility is the ability of vessel to stretch
| - compliance is the ability of a vessel to stretch and hold volume
55
What is the equation for distensibility and compliance
- D = change in volume/ (change in pressure x initial volume)
- C = change in volume / change in pressure
- C = distensibility x initial volume
56
What is the relationship of change in volume and change in pressure in systemic arteries and veins
- Sys. Arteries a small change in volume = large change in pressure
- veins = large change in volume = small change in pressure
57
What are 8x more distensible and ____ more compliant than systemic arteries
Veins/ 24x
58
Local blood flow is regulated in proportion to _______ in most tissues
Metabolic demand
59
Short term control of blood flow involves what?
Vasodilation, vasoconstriction of precapillary resistance vessels
60
Long term control of blood flow involves
Change in tissue vascularity
- formation or dissolution of vessels
- vascular endothelial growth factor and angiogenic
61
What is the role of arterioles in control of flow (3)
- act as integrator of multiple input
- richly innervated by SNS vasoconstrictor fibers and have alpha receptors
- effected by local factors vasodilators, circulation substances
62
What constricts arterioles
SNS
63
What dilates arterioles
NO,CO, decreased O2, local vasodilators
64
Vasodilation equals what in R and F
Vasodilation = decrease in R and increase in F
65
Vasoconstriction has what effect of R and F
Increase R, decrease F
66
What is the local vasodilator theory
Active tissues release local vasodilator (metabolites) which relax vascular smooth muscle
67
Oxygen demand theory
As tissues use up oxygen, vascular smooth muscle cannot maintain constriction
68
What is autoregulation
The ability to keep blood flow constant in the face of a changing arterial BP
- most tissues show this
69
In the kidney what two things are autoregulated
Renal flow and glomerular filtration rate (GFR)
70
Control flow (long term) changes tissue what?
Vascularity
71
Under which control of flow does angiogenesis takes place
Long term
72
What is ateriogenesis
Shear stress caused by enhanced blood flow velocity associated with partial occlusion
73
What are angiogenic factors
- small peptides that stimulate growth (VEGF)
| - first isolated from tumors (if blocked, they can’t grow)
74
What type of endothelium up regulates expression of monocyte chemoattractant protein 1 (MCP-1)
Stress activated endothelium
75
What does stress activated endothelium attract that invade arterioles
Monocytes
76
What is hypoxia’s affect on VEGF
It causes a release of VEGF
77
In response to hypoxia what enhances the production of VEGF
Partly mediated by adenosine
78
What does VEGF stimulate
- Capillary proliferation
| - development of collateral arterial vessels
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What would the effect of hyperactive SNS be on tissue vascularity
May compromise blood flow by vasoconstriction
80
What is vasculogenesis
Mesenchymal cell differentiation into endothelial cells
81
What is angiogenesis and what is unique about it
Formation of new blood vessels by sprouting from pre existing small vessels usually lacking developed tunica media
82
What is arteriogenesis and what is unique about it
Rapid proliferation of pre-existing collateral vessels with fully developed tunica media
83
What are mechanical triggers for angiogenesis
- hemodynamic
| - shear stress
84
What chemically triggers angiogenesis
Hypoxia, NO
85
What molecularly triggers angiogenesis
- decrease in glucose = increase in VEGF
- inflammation
- angiogenic growth factors (fibroblast, VEGF, PLGF, angiopoietin)
86
3 methods for therapeutic angiogenesis
- protein therapy
- gene therapy
- cellular therapy
87
Vasoactive role of endothelium
- release prostacyclin (PGI2)
- releases nitric oxide (NO) (healthy endothelium)
- releases endothelium (damaged endo)
88
What is prostacyclin (PGI2) role
- inhibits platelet aggregation
| - relaxes vascular smooth muscle
89
What does the release of NO do on endothelium
- vasodilator
| - stimulated by shear stress and ACh
90
How does endothelin affect endothelium
- constricts vascular smooth muscle
| - contribute to vasoconstriction when endo is damaged by hypertension
91
Where does the bulk of exchange take place
Microcirculation of capillaries
92
What are the mechanisms of exchange in microcirculation
Diffusion, ultrafiltration, vesicular transport
93
What is oxygen uptake/utilization
The product of flow (F) times the arterial venous oxygen difference
O2 uptake = (F)(A-VO2 difference)
94
What is functional vs non functional flow
- Functional/ nutritive flow (F) is associated with increased O2 uptake/utilization
- O2 uptake must change to be functional/ nutritive
95
What does non nutritive flow do
Increases are associated with shunting of blood through a bed
96
How does passive diffusion take place in capillaries
Permeability and concentration gradient
97
How does ultrafiltration take place in capillary exchange
- Bulk flow through a filter (capillary wall)
| - starling forces (hydrostatic or colloid osmotic P)
98
How does vesicular transport take place in capillary exchange
Large MW nonlipid soluble substances
99
Hydrostatic P gradient favors what kind of filtration
High (17mmHg) to low (interstitial avg = -3mmHg)
100
Colloid osmotic P favors what type of flow
Low to high
- capillary avg 28mmHg
- interstitial avg 9mmHg
101
What is the equation for net filtration
NFP = (CHP-IHP) - (CCOP-ICOP)
102
What is a function of the protein concentration
Colloid osmotic pressure
103
What is the discrepancy due to between calculated and actual colloid effect
Donnan effect
104
What is the donnan effect
- Increases the colloid osmotic effect
| - large MW plasma proteins carry negative charge attracting positive ions increasing osmotic effect by 50%
105
What does reflection coefficient express
It expresses how readily protein can cross the capillary wall ranging between 0 to 1
106
How is reflection coefficient evaluated
0 to 1
0 = no colloid effect, proteins cross wall freely,
1= all colloid proteins reflected, none cross, full colloid effect
107
No true lymphatic vessels found where
- superficial skin
- CNS
- endomysium of muscle
- bones
108
What does the thoracic duct drain
Lower body, left side of head, arm, and part of chest
109
What does right lymph duct drain
Right side of head, neck, right arm, part of chest
110
What acts as a functional lymphatic system in the CNS
Plasma filtrate & escaped substances in
perivascular spaces returned to the vascular
system in the CSF via the arachnoid villi which
empties into Dural venous sinuses
111
Where is most of the formation of lymph from?
2/3 of all lymph from liver and intestines
112
What promotes lymph formation
Any factor that increases filtration and or decreases reabsorption will increase lymph formation
113
What is the total lymph flow rate
120 ml/hr, 100 from thoracic duct, 20 from right duct
114
What is the function of lymphatics
- return lost protein to vascular system
- drain excess plasma filtrate from ISF
- carry absorbed substances/nutrients from GI tract
- filter lymph at lymph nodes (defense)
115
What are lymph noes sinuses lined with?
Tissue macrophages
116
What is arterial blood pressure created by
Interaction of blood with vascular wall
117
What is the equation for arterial bp
Art BP = CO (inflow) x TPR (outflow)
118
Where is greater than 1/2 of TPR located
Systemic arterioles
119
What happens during systole
Left ventricular output (SV) is greater than peripheral runoff = total blood volume rise = art. Bp increases
120
The arteries are distended during systole T/F
True
121
What happens during diastole
- While left ventricle is filling arteries are recoiling, this maintains perfusion to tissue beds
- total blood volume in arterial tree decreases causing art. Bp to fall to minimum value
122
What is hydraulic filtering
Stretch (systole) and recoil (diastole) of arterial tree that normally occurs during the cardiac cycle
123
What is hydraulic filterings effect?
This phenomenon converts an intermittent output by the heart to steady delivery at the tissue beds and saves the heart work
124
As distensibility of the arterial tree decreases, what happens to hydraulic filtering
It is reduced therefore work load on the heart is increased
125
What is the maximum pressure in the systemic arteries
Systolic bp
126
When does pressure peak in systolic bp
As blood is ejected from left ventricle into aorta
127
What happens faster, inflow volume of LV or peripheral runoff
Inflow volume from LV causing arterial P to increase
128
What is the minimum pressure in systemic arteries
Diastolic bp
129
How low the pressure falls in diastolic pressure is dependent on what 2 factors
- cycle length inversely proportional to DBP
| - total peripheral resistance (TPR) proportional to DBP
130
What happens to DBP during exercise
DBP may not change much due to decrease CL is offset by decrease in TPR
131
How is mean arterial bp configured
MAP = 1/3 pulse pressure + DBP (approx)
132
What do most post ganglionic SNS terminals release
Norepinephrine
133
What is the predominant receptor type of SNS
Alpha
134
What is alpha receptors response in SNS
- constriction of smooth muscle, raise art. Bp, increase venous return
About 1L of blood can be mobilized from splanchnic veins during exercise
135
SNS causes widespread _____ causing _____ in blood flow with what 3 exceptions
- vasoconstriction/ decrease
| - brain, lung, heart
136
What is critical closing pressure
As arterial pressure falls, there is critical pressure below which flow ceases due to closure of arterioles
137
What is required to keep arterioles from closing completely
Critical luminal pressure
138
Vascular tone is proportional to what?
Critical closing pressure
139
If cardiac output is stopped what happens
Arterial pressure will fall and venous pressure will rise
140
What is mean circulatory filling pressure
MCFP = equilibration pressure where arterial bp= venous bp
141
What can prevent equilibration pressure
Closure of arterioles (critical closing pressure)
142
What is mean circulatory filling pressure responsible for
For pressure gradient driving peripheral venous return
143
As central venous pressure increases what happens to venous return
Decreases
144
If MCPF = CVP what happens to venous return in the vascular function curve
Goes down to 0
145
In the cardiac function curve what happens as central venous pressure increases
Cardiac output increases due to both intrinsic and extrinsic factors
146
What is central venous pressure
The pressure in central veins (sup/inf vena cava) at entry to right atrium (CVP = right atrial pressure)
147
What is the vasomotor center
Collection of neurons in medulla and pons
148
What are the four main regions of the vasomotor center and what do they do
- Pressor center = increases bp
- depressor center = decreases bp
- sensory area = mediates baroreceptor reflex
- cardioinhibitory area = stimulates CN. X
149
Where is the pressor center of VC located and what are its effects
Anterolateral portion of upper medulla has norepinephrine projections to intermediolateral horn cells for vasoconstriction and stimulation of cardiac activity
150
What drives SNS outflow from IML
Tonically active pressor center
151
What does the depressor center do
- fibers project into/inhibit pressor center
- ant. Lower MO
- effects by inhibiting presser center to vasodilate and decreases cardiac activity
152
What does the sensory area of the VC do
- Postlat. Portions of pons and medulla in nucleus tractus solitarius
- receive input from CN IX and X
- outputs both on pressor and depressor centers
153
What mediates baroreceptor reflex and how
Sensory area of VC by inhibiting pressor center, and lowers bp
154
What does the carrdioinhibitory area do of the VC
- Located medially next to dorsal motor nucleus of vagus
| - transmits impulses to DMNV inhibiting heart activity
155
What does sympathetic vasoconstrictor tone do
- due to pressor center input
- 1/2 to 2 IPS
- maintains normal arterial bp
156
Does short term or long term control involved in the nervous system effect on vascular smooth muscle
Rapid short term
157
What is long terms control on bp
Dominated by the kidneys for renal body fluid balance
158
What is contents vs containner
Control of bp is accomplished by either affecting vascular tone or blood volume
- contents= blood volume
- container=blood vessels
159
Where are baroreceptors abundant
Carotid sinus, arch of aorta
160
When are baroreceptors stimulated
When stretched, inhibits pressor center via CN IX,X and NTS
161
What are baroreceptors effects
Vasodilation, decreased cardiac output
162
What are baroreceptors more sensitive to
Changing P
163
What is the buffer function of baroreceptors
Buffer change in bp to change in blood volume = during normal cardiac cycle / buffer change in bp due to. Change in body position
164
Why does the barorecptor have to reset
Lack of long term control due to adaptation
165
Where are low pressure baroreceptors and what do they do
Located in atrial walls and pulmonary arteries
| - minimize arterial pressure changes in response to blood volume changes (mainly sense on low pressure side)
166
What does the bainbridge reflex do
Increases heart rate from stretch on atrial wall
167
What are the effects of releasing of atrial natriuretic peptide after stretch on atrial wall
Diuretic, natriuretic, vasodilator
168
What is the barorecptors reflex after low pressure stretch on atrial walls
Decreased heart rate, increased urine production (decreases SNS and ADH)
169
Increased ECF in _____ will cause AP to rise
Renal body fluid system
170
What is renal body fluid system
- arterial pressure control
- increase ECF cause AP to rise
- kidneys excrete ECF
171
Determinants of long term arterial pressure
- shift of renal output curve for water and salt
- level of water/salt intake line
- increased TPR will not create long term elevation of bp if fluid intake and renal function don’t change
172
What supply the glomerular capillaries in the kidney
Afferent arterioles
173
Where does filtration take place in kidney
Glomerular capillaries
174
What do efferent arterioles do in the kidney
Drain the glomerular capillaries and give rise to perituubular capillaries where reabsorption takes place
175
What are vasa recti in the kidney
Specialized peritubular capillaries associated with juxtamedullary nephrons
176
What happens in renal control of bp
When ECF rises the AP rises, the kidney excretes more fluid and brings pressure to normal
177
The higher the gain the more effective the ____
Control system
178
What has chronic effect of AP
SNS, renin angiotensin system, aldosterone, ADH, ANP
179
Hormones that decrease renal blood flow
Norepinephrine, epinephrine, angiotensin 2
180
Hormones that increase renal blood flow
Prostaglandins (E and I)
181
What is tobuloglomerular feedback
Monitors NaCl in the macula densa of the distal tubule
182
What is increased renin has what effects on angiotensin 2 and efferent arteriole resistance
Increased renin increases angiotensin 2 and increases efferent arteriole resistance
183
Decrease of NaCl does what in macula densa
Causes dilation of afferent arteriole
184
What is the source of renin
Smooth muscle cells in afferent arteriole
185
What is renin stimulated by
- decrease in perfusion pressure
- +SNS
- decrease NaCl deliver to macula densa
- hormonal stimulation (thyroid/growth hormone)
186
What is renin
An enzyme the catalyses the formation of angiotensin 1 (10 amino acids) from angiotensinogen (liver)
187
Where does angiotensin 1 turn to angiotensin 2
Occurs primarily in lung via angiotensin converting enzyme associated with pulmonary endothelium
188
What are the functions of angiotensinn 2
Stimulate adrenal cortex to secrete aldosterone, release of ADH/vasopressin/kidney
189
What stimulates thirst/drinking behavior at the level of hypothalamus
Angiotensin 2
190
What is the role of breathing in BP control
Slow breathing (6/min) increases arterial baroreflex sensitivity
191
What are the effects of antioxidants on BP
- NO from endothelium relaxes smooth muscle
- NO is rapidly inactivated by superoxide radicals
- increasing antioxidants reduces free radicals allowing NO effect to last longer = lowering bp
192
What is serotonins effect at CNS
May act at CNS to inhibit reflex SNS activation
193
NO may act centrally to inhibit what?
Sympathetic nerve activity
194
Nitric oxide may promote what in hypotension
Promote bradycardia and hypotension
195
Where does gas exchange take place for a fetus
The placenta, pulmonary blood flow is minimal
196
How does blood get to the placenta
It flows via umbilical arteries which is a branch off the anterior iliac arteries
197
How does blood return to the fetus from the placenta
Umbilical veins
198
What are the fetal shunts and their pathways
- ductus arteriosis (DA) = SVC>RA>RV>pulm trunk>DA>aorta
- foramen ovale (FO) = IVC>RA>FO>LA>LV>AORTA
- ductus venosus(DV) = umbilical vein>DV>IVC, portal vein>DV>IVC
199
What part of fetal shunts allow blood to bypass lungs
ductus arteriosis, and foramen ovale
200
What is ductus venosus’ role in fetal shunts
DV allows umbilical and portal blood to bypass liver
201
Oxygen saturation in fetal blood
Most in umbilical vein, then IVC, Then aorta
202
What happens after increased blood flow through lungs and liver after birth
Pulmonary vascular resistance decreases = decreased RVP and pulmonary arterial bp
203
What happens when there is a loss of blood flow through placenta
It doubles the systemic vascular resistance = increased LAP,LVP, and aortic bp
204
What closes at birth
Foramen ovale, ductus arteriosis, ductus venosus
205
How does the foramen ovale close
Due to reversal of pressure gradient between RA and LA, flap closes
206
How does the ductus arteriosis close
Reversal of flow from aorta to artery and increased oxygen levels cause constriction of smooth muscle
207
What happens when ductus venosus closes
Allows portal blood to perfuse liver sinuses
208
Why is there low pressure in aorta of fetus
Due to low TPR because of placenta umbilical arteries
209
How many shunts are there to bypass lungs in fetus
Two right to left shunts
210
What shunts most of the blood returning to heart via IVC
Foramen ovale from IVC to left atrium
211
What shunts most of blood returning to heart via SVC
Ductus arteriosis
212
How much is CO increased during exercise
5-6 fold
213
What are SNS effects after cerebral cortical activation
- vasoconstriction of arterioles to decrease flow to non active tissues
- vasoconstriction of veins to increase MCFP which increases venous return
- stimulation of heart (increase HR,SV) increases CO
214
What part of CV changes during exercise is not mediated by SNS
TPR decreases due to vasodilation in active muscle
215
What is SNS stimulation during exercise due to
Cerebral cortex stimulation, reflex signals from joint proprioceptors, chemoreceptor signals originating in active muscle
216
T/F SNS induces local metabolic vasodilation of the heart
True
217
What SNS stimulation decreases blood flow
Stimulation of pre-capillary resistance vessels (organs/inactive muscle)
218
How does venous return increase after SNS stimulation
SNS stimulation of veins cause constriction mobilizing blood out of veins redistributing blood volume
219
What helps during SNS stimulation via vascular smooth muscle
Vascular smooth muscle in walls of arteries help maintain slightly increased bp during exercise
220
What tissues escape SNS vasoconstriction
Heart, brain, lungs
221
What is equation of pulse pressure and how does it change in exercise
PP=SBP - DBP
Increased PP (increaseSBP>increaseDBP)
222
How does increased venous return help in exercise
Increase frequency and depth of respiration producing cyclic negative thoracic pressure
223
How is increased blood flow to active muscle mediated
Not by SNS but local release of tissue metabolites in response to increase in metabolism ‘local vasodilators’
224
Blood flow at rest and exercise
Rest CO = 5.9 L/min
| Exercise = 24L/min
225
Exercise increases all CV endpoints except ____
TPR
226
What is oxygen debt
If energy needed in exercise can’t be met by oxidative phosphorylation, O2 debt occurs
227
O2 debt equation
Energy consumed during exercise - E supplied by oxidative metabolism
228
Respiration after exercise remains elevated, why?
To repay O2 debt of about 11.5 L restoring metabolite levels and lactate by glycolysis
229
The phosphocreatine system in exercise
Uses ATP, creatine phosphate lasting 8-10 seconds
230
The glycogen lactic acid system
1.3-1.6 min
| Utilizing glycolysis
231
The aerobic system during exercise
Utilizes oxidation of glucose, occurs in mitochondria with sufficient O2 - (this is unlimited with O2 and nutrition)
