Vascular Phys Flashcards
(159 cards)
0
Q
Circulatory nutrient delivery
A
rapid delivery to within 10-20 micrometers of most cells
1
Q
Circulatory Functions
A
- Nutrient & waste exchange
- Electrolyte & H2O balance
- Body temp regulation
- Delivery of hormones
- Delivery of defense mechanisms
2
Q
Microcirculation consists of
A
arterioles, capillaries, venules
3
Q
Microcirculation location
A
within organs
4
Q
arterioles =
A
stopcock of organ blood flow
5
Q
Veins are
A
reservoir of blood in the body
6
Q
What happens when veins constrict?
A
there is an increase in venous return
7
Q
% Total Blood Volume in Pulmonic Circulation
A
9%
8
Q
% Total Blood Volume in Systemic Circulation
A
84%
9
Q
% Total Blood Volume in Heart
A
7%
10
Q
Cardiac Output Redistributed for Changes in Metabolic Demands based on..
A
reconditioning and non-reconditioning organs
11
Q
Reconditioning Organs
A
have role in “reconditioning” blood to improve it for entire body
ex: GI tract, Kidneys,
12
Q
amount of blood received by reconditioning organs
A
more blood than necessary for metabolic needs
13
Q
Reconditioning organs can..
A
tolerate reduction in blood flow when need be because they get more than needed
14
Q
Non-reconditioning Organs
A
ONLY receive exact amount of blood they need to live
ex: brain, heart, skeletal muscle, bone
15
Q
Hemodynamics
A
study of physical factors that determine blood flow & blood pressure in the body
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Q
Physical Factors of Hemodynamics
A
pressure, velocity, flow, resistance, diameter, velocity
17
Q
Systemic Pressure
A
high pressure
18
Q
pulsatile blood pressure
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increase and decrease of artery blood pressure (125/80)
19
Q
pulsatile blood pressure in arteries
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occurs because of cardiac systole
20
Q
pulsatile blood pressure in capillary beds is based on:
A
- Distensibility of large arteries
2. Frictional resistance of small arteries & arterioles
21
Q
Why is pulsatile blood pressure in capillaries important?
A
It provides constant movement & supply of blood in organs & allows for constant exchange.
22
Q
Pulmonic pressure
A
low pressure
23
Q
Why is pulmonic pressure low pressure?
A
less resistance to overcome (shorter tube length)
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Why do you want a low pressure in pulmonic circulation?
high pressure would drive fluid out of capillary beds & into the lung tissue
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PVR (Pulmonary Vascular Resistance)
sum of resistance of vasculature in pulmonary circulation
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SVR (Systemic Vascular Resistance)
sum of resistance of vasculature in systemic circulation
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PVR compared to SVR
PVR <<<<< SVR
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Velocity of blood
varies inversely as a function of cross-sectional area (CSA)
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What happens if CSA increases?
Velocity decreases & get maximal exchange in capillaries
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What happens if CSA decreases?
velocity increases and amount exchanged decreases
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Vena Cava velocity vs. aorta velocity
vena cava's velocity is lower than aorta because it's a bit larger than the aorta
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Flow through all levels of circulation
constant
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Flow velocity varies
as a function of CSA of each level
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Flow Velocity =
particle movement (distance) per unit time
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Flow rate
rate of displacement of volume of a fluid
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Flow depends on
pressure gradient and vascular resistance
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Pressure gradient is the...
primary force of blood flow
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Flow is
independent of absolute/individual pressure levels
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Resistance depends on
vessel radius, vessel length, and blood viscosity
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Vessel Radius
changes in the body as necessary
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blood viscosity
friction of molecules in blood stream
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What changes to influence resistance?
vessel radius
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What doesn't change to affect resistance?
vessel length and blood viscosity
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What happens if you increase vessel radius 2X?
you decrease resistance 16X & increase flow 16X
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Viscosity
varies as a function of hematocrit
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normal hematocrit
40% total blood volume
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normal blood viscosity vs water viscosity
3x greater than water's
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If blood viscosity is 3X higher than water's,
resistance is higher & pressure must increase 3X to push blood through vasculature
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Types of Changes in Viscosity
1. Anemia
| 2. Polycythemia
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Anemia
low RBC count
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anemia effects on circulation
decreases viscosity, decreases resistance, decreases pressure, increases venous return, increases cardiac output, causes hypoxia (decreased O2 delivery), which increases CO more,
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What happens if you're anemic and CO can't keep up with metabolic needs?
heart failure... death!
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Polycythemia
high RBC count
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Polycythemia's effect on blood
increases viscosity, increases resistance, increases pressure, decreases flow, decreases venous return, increases blood volume
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increased blood volume in polycythemia
offsets the decrease in venous return caused by polycythemia which maintains normal CO
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Vessel Arrangements
1. Parallel
| 2. Serial
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Parallel Vessel Arrangements
occurs in most systemic vascular beds
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Parallel Vessel Arrangement affect on Resistance
Total R < R of individual component in parallel arrangement
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benefits of parallel vessel arrangements
1. Reduces SVR
2. Blood flow is independently adjusted
3. Blood flows at similar perfusion pressure
4. Arterial blood is of identical composition
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Significance of arterial blood being of identical composition in parallel vessel arrangements
organs see "fresh" blood. not blood that's passed through other organs first
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Serial Vessel Arrangement occurs in
splanchnic & renal beds
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Serial Vessel Arrangement's affect on resistance
high resistance
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Serial Vessel Arrangement's affect on pressure
drop in pressure gradient as you move across each bed
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Patterns of Blood Flow
1. Laminar
| 2. Turbulent
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Laminar Blood Flow
- normal
- streamlined & straight
- silent
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Turbulent Blood Flow
- mostly abnormal
| - noisy
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Turbulent blood flow used diagnostically for
- murmurs
| - bruits
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murmurs
cardiac valvular lesions
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bruits
vessel stenosis, shunts
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critical velocity
where flow switches from laminar to turbulent
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Reynolds Number
measure of tendency for turbulence to occur
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Example of Bruit
```
arteriovenous fistula (joining of artery & vein)
decrease in BP => increased CO to accomodate
```
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Turbulence is created by...
1. Large vessel diameter (aorta)
2. Large Vessel branch points
3. High velocity (anemia)
4. Obstruction (atherosclerosis)
5. Low viscosity (anemia)
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Turbulence frequencies
high in aorta
| low in small vessels
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Role of Arteries in Vascular System
to convert intermittent output of heart to steady flow into capillaries
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Arteries are..
- elastic
- distribution channels
- pressure reservoirs
- contain little resistance to flow
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Arterioles are...
muscular
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Arterioles function
control blood flow through capillaries
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arterioles' resistance
high.
| have greatest amount of R in system to control blood flow
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Compliant Arteries
- in young, healthy animals
| - very elastic arteries
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Compliant Arteries allow
arteries to behave as pressure reservoirs (aka can swell)
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Rigid Arteries are...
- in older animals
| - have lost some elasticity
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Rigid arteries produce
high afterlaod
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Effect of rigid arteries' loss of elasticity
loss of function as pressure reservoir in circulatory system
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Flow in Rigid Arteries
stops in diastole
| occurs only in systole
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Flow in Compliant Arteries
continues during systole & diastole
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Effect of discontinuous flow in rigid arteries
intermittent flow occurs in capillary beds, so exchange isn't continuous
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Pulse Pressure =
systolic BP - diastolic BP = SV/arterial compliance
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Pulse pressure function
sharp upstroke in P (systole) -> P starts decreasing ->aortic valve shuts -> slight increase in P -> exponential decline in P (diastole) -> REPEAT
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Abnormal pulse pressures
can be used diagnostically
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Arteriosclerosis Pulse Pressures
high systolic P. Normal diastolic P. normal dichrotic notch
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Aortic Stenosis Pulse Pressures
low, flat systolic P
normal diastolic P
no/small dichrotic notch
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Patent Ductus Arteriosus Pulse Pressures
- High systolic P
- Low diastolic P
- Normal dichrotic notch
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Aortic Regurgitation Pulse Pressures
- High Systolic P
- Low Diastolic P
- No dichrotic notch
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Primary job of heart
control MAP
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Barrow reflex starts when
MAP decreases
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Effect of Barrow Reflex Starting
Increases CO, Increased systolic P
thereby maintaining normal BP
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Arterioles Job
control blood flow in capillaries
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Arterioles provide ___ resistance
greatest resistance to control flow
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Arterioles control of resistance
independently control resistance by smooth muscle contraction
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Why is independent control of R important for arterioles?
It permits arterioles to have precise control of flow into individual capillary beds & aids in BP regulation
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Result of constricting arterioles
increase MAP upstream
| decrease MAP downstream
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Result of dilating arterioles
Decrease MAP upstream
| Increase MAP downstream
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basal tone
allows dilation under basal conditions & maintains BP
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How does basal tone work?
1. Myogenic stretch
| 2. Basal Norep. release
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Myogenic stretch
stretch Ca channels open & increase cytosolic [Ca]
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Opening of stretch Ca channels occurs
when P is put on walls, & the walls stretch
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Why does more cytosolic [Ca] increase basal tone?
Ca is essential for smooth muscle contraction
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Basal norep. release occurs
at sympathetic nerve fibers
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Basal norep. binds
to adrenergic receptors & leads to vessel contraction/constriction
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Independent Arteriolar Control caused by
systemic and local factors
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Extrinsic Control/Systemic Responses done by:
1. Neural influence (sympathetic N.S.)
| 2. Humoral Factors
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Job of Extrinsic Control/Systemic Responses
regulate blood pressure
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Intrinsic Control/Local Control done by:
1. Metabolic Factors
2. Endothelium-mediated
3. Myogenic Responses
4. Shear stress
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Job of Intrinsic Control/Local Control
determine cardiac output distribution
aka determines which organs get which blood
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Intrinsic Control/Local Control regulates:
1. Autoregulation
| 2. Reactive Hyperemia
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Metabolic Factors are important in
brain, heart, skeletal muscle
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Intrinsic Control vs Extrinsic Control
Intrinsic OVERRIDES extrinsic
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Constriction of Arterioles caused by
sympathetic nerves stimulate smooth muscle contraction
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How does sympathetic innervation cause smooth m. contraction?
1. Releases norep. into neuromuscular junction
2. Norep. binds to a-1 adrenergic receptors
3. Ca released & contraction occurs
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What happens if you increase sympathetic nerve activity?
Increase norep. release => VASOCONSTRICTION => increased R => decreased flow
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What happens if sympathetic nerve activity decreases?
decreases norep. release => VASODILATION => decreased R => increased flow
123
Exception to sympathetic nerve stimulation of smooth m. contraction
brain
124
Why is the brain the exception to smooth m. contraction by sympathetic nervous stimulation?
Brain has no a-1 receptors.
125
How do the brain's arterioles contract?
use local mechanisms to maintain constant blood flow
126
Parasympathetic N.S. & Arterioles
basically has no effect
| dilates arterioles in salivary glands, GI glands, & genetalia
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Humoral Factors
- Norep. for a-1 receptors in most arteriolar smooth m.
| - Ep. for b-2 receptors
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Epinephrine for B-2 receptors Function
stimulates arterioles of heart & skeletal m. to dilate
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Epinephrine =
"breaks" for cardiovascular system
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How does epinephrine work?
It works with other local mechanisms to counteract a-1 constriction
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Angiotensin II
potent vasoconstrictor
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Vasopressin
potent vasoconstrictor
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Angiotensin II & Vasopressin function
maintain amount of salt that kidneys retain by being released into blood stream
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Metabolites cause...
local vasodilation
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Active hyperemia
increased blood flow to highly active tissues
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Reactive Hyperemia
increased flow to tissue AFTER flow is acutely blocked
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How does reactive hyperemia work?
occlusion occurs & increases metabolite build up. When occlusion is released, flow increases to remove metabolites => longer removal time based on occlusion time
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exercise effect
combination of occlusion & exercise increases [metabolite] => higher increase in flow
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Local Vasoactive Mediators come from
endothelium
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Types of local vasoactive mediators
1. Vasodilators
| 2. Vasoconstrictors
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Vasodilators
NO, prostacylin, EDHF
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Vasoconstrictors
endothelin, Angiotensin II, prostaglandins
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Sheer Stress
longitudinal frictional resistance between blood & vessel walls
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Myogenic Mechanism
a smooth muscle phenomenon
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Example of Sheer Stress mechanism
aids in increasing flow in tissues w/ increased metabolic demand by dilating vessels.
small arterioles dilate to metabolites well => increased sheer stress in small upstream aa. => NO release => dilation of small aa.
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How myogenic contraction works?
changes in transmural pressure alters contractile states of arterioles
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Myogenic Mechanism resulting from ^ pressure
^P => opening of stretch activated Ca channels => ^ Ca influx => ^ contraction => decreased r => decreased flow
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Autoregulation of Flow
maintains normal organ flow despite changes in arterial pressure
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What organs autoregulate best?
brain, heart, kidneys
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Autoregulation of Flow Mediated by:
myogenic and metabolic responses
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If perfusion pressure decreases,
flow decreases & therefore need to decrease R to ^ flow to normal levels
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When perfusion pressure decreases what causes a decrease in R to bring flow back to normal?
sympathetic discharge
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Sympathetic discharge effects
no change in pressure. arterioles dilate. Resistance decreases.
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Myogenic response to decreased perfusion pressure
decreased stretch, less Ca entry, increased relaxation (DILATION)
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Metabolic response to decreased perfusion pressure
increased [metabolite] => increased dilation to get more out
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Increased perfusion pressure effects
increased flow meaning R needs to increase to bring flow back DOWN to normal levels
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Myogenic response to increased perfusion pressure
^ stretch, ^ Ca entry, ^ contsriction, ^ R, decreased flow
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Metabolic response to increased perfusion pressure
decreased [metabolite], ^ constriction to keep metabolites at normal levels in the region
