Cardiovascular Physiology Blood Vessels and Blood Pressure and Capillary Exchange Flashcards
describe veins
-few layers of SM and CT
- few elastic layers
-wide lumen
describe arteries
-many layers of SM and CT
-several elastic layers
what makes up venules
CT and endothelium
what makes up arterioles
SM cells and endothelium
what is vascular tone created by
level of vascular smooth muscle contraction
what determines radius of vessel lumen
vascular tone
what does increased vascular tone do to vasoconstriction, lumen diameter, and resistance
increased vasoconstriction and decreased lumen diameter and increased resistance
what is vascular tone modified by
-paracrines from endothelial cells such as NO and prostacyclin and endothelin-1
-autonomic NS
what does NO and prostacyclin do to tone and SM
decreases tone and relaxes SM
what does endothelin-1 do to tone and SM
increases tone, contracts SM
what does sympathetic NS do to tone
increases
where is the parasympathetic NS found in blood vessels
only penis and clitoris
do arteries and arterioles have basal tone? veins/venules?
arteries- yes
veins - no
what is vascular tone in arteries mediated by
paracrines secreted by endothelial cells and tissue
-tonic activity of sympathetic motor neurons
do arteries vasodilate or vasoconstrict from rest
both
do veins vasodilate or vasoconstrict from rest
only vasoconstrict
what does abnormal arterial tone do to BP
can cause hypertension
what is compliance
how easy a structure stretches
describe volume and pressure in high compliance vessels such as veins
can have large changes in volume with little change in pressure
describe volume and pressure in low compliance vessels such as arteries
will have large changes in pressure with small changes in volume
what does SM contraction do to compliance
decreases it
what does increase in pressure do to VR,SV,CO,and EDV
increases everything
when does pulsation of arterial vessels disappear and why
by the capillaries due to decreasing elastic/collagen tissue and increasing resistance as you move through arteries and capillaries
what is damping
smoothing out of blood flow/pulsation in arteries
what is the driving force to get blood to capillaries (in arteries)
63 mmHg
what causes the dicrotic notch
elastic recoil of aorta
what is MAP (number)
93 mmHg
what does elastic recoil prevent
arterial diastolic pressure from dropping to ventricular diastole pressure. essential to maintain driving pressure in systemic circulation
what happens to MAP with arteriosclerosis
decreases it because of stiffening of arteries
how is pulse pressure calculated
systolic BP - diastolic BP
what are the most important factors determining the magnitude of the pulse pressure
-stroke volume
-arterial compliance
what is the relationship between PP and SV
direct
what is the relationship between PP and compliance
indirect
what does reduced SV do to MAP
decreases it
what is MAP definition
average driving pressure in systemic circulation to move blood through the blood vessels
what does hypertension do to MAP
increases it
what is elevated BP considered
120-129/less than 80
what is high BP stage 1 considered
130-139/80-89
what is high BP stage 2 considered
140 or higher/90 or higher
what is hypertensive crisis considered
higher than 180/higher than 120
what are factors that influence MAP
-flow in and out of systemic arteries
- total blood volume
- distribution of blood in circulatory system
what is the formula for flow in systemic arteries
CO (HR x SV)
what is the formula for flow out of systemic arteries
TPR
what is the formula for TPR
the sum of resistance in all arterioles
what happens to MAP if flow in > flow out
increased
what is formula for MAP with TPR
MAP = CO x TPR
what percentage of blood is found in arteries and veins
11% in arteries and 60% in veins
what is resistance of the system to blood flow determined by
diameter or arterioles
what regulates arteriolar diameter
-autoregulation
-local control
- systemic/reflex control
what does autoregulation do
assures blood flow to tissues match tissue demands
what does local control of arteriolar diameter do
match tissue blood flow to metabolic demands
what is the equation for tissue flow in arterioles
MAP/Resistance of tissues
what does systemic/reflex control do to arteriolar diameter
maintain MAP to assure adequate blood flow to the brain and heart
what overrides the other in arteriolar diameter regulation: local or systemic
systemic control
what controls flow into capillaries
resistance of arterioles
what is the mechanism of myogenic autoregulation
increased MAP -> increased arteriolar blood flow -> arteriolar stretch -> open mechanically gated Na+ channel in VSM -> depolarizes membrane -> opens voltage gated Ca++ channels in VSM -> Ca2+ entry and binds to calmodulin -> activates myosin light chain kinase -> increased myosin ATPase activity -> VSM contraction -> vasoconstriction -> decreased radius -> increased resistance -> decreased tissue flow
what does increased tissue metabolism do to O2,CO2, H+,K+
decreased O2, increased CO2, increased H+, increased K+
what is active hyperemia
process in which an increase in tissue blood flow accompanies an increase metabolic activity
what do arterioles do with increase in tissue metabolism
dilate
what is reactive hyperemia
increased in tissue blood flow following a period of low perfusion
what happens when blood flow to a tissue is occluded and paracrines accumulate in interstitial space
-decrease in O2
-increase in CO2
-increase in H+
what does hypoxia do to endothelial cells
stimulates them to secrete NO and NO accumulates in interstitial space
what happens to paracrines once occlusion is removed
paracrines cause vasodilation and increase in tissue blood flow until paracrines washed away and arteriolar diameter returns to resting state
what happens to paracrines once occlusion is removed
paracrines cause vasodilation and increase in tissue blood flow until paracrines washed away and arteriolar diameter returns to resting state
what are the vasodilating paracrines
-CO2
-H+
-adenosine
- K+
- prostaglandins
-bradykinin
-NO
what are the vasoconstricting paracrines
-O2
-endothelin
-thromboxanes
what does NE bind to and do in SM
alpha 1 and causes vasoconstriction
what does EPI bind to and do in SM
alpha 1 to cause vasoconstriction and beta 2 to cause vasodilation
what other hormones are vasoconstrictors
ADH and ANGII
what other hormones are vasodilators
ANP
what is the mechanism of ANP
increased BV -> atria -> increased ANP -> kidney -> increased Na+ and water excretion -> decreased blood volume
what is the pressure in veins
10 mmHG
what tunics do veins have
all 3
what is another name for veins
capacitance vessels
what are the mechanisms that support venous return
-venous valves
- respiratory pump
- skeletal muscle pump
- venoconstriction
what are varicose veins
veins that have become dilated and tortuous resulting incompetent valves
what does venous return do to EDV and SV
increases both
why does dampening occur in arterioles
highest resistance in arterioles
what is the pressure in the capillaries
20 mmHg
what are the mechanisms of capillary exchange
-movement of fluid and dissolved substances via bulk flow
-transcytosis and transepithelial transport
- simple diffusion
what is the metarteriole/thoroughfare channel
most direct route between arteriole and venule
what does the metarteriole/thoroughfare channel contain
intermittent smooth muscle
what do precapillary sphincters do
control entrance to capillaries
what are arteriovenous anastomosis and what does it do
direct connection between arteriole and vein but no exchange. it allows WBCs and large proteins to move from arteriole side to venule side
what is the rate of fluctuation of metarteriole and precapillary sphincters controlled by
concentration of oxygen in tissue
what happens to the SM if concentration of O2 is low
smooth muscle is more relaxed state and blood takes convoluted path through capillary bed
what happens to the SM if concentration of O2 is high
smooth muscle is more contracted state and blood takes more direct path through capillary bed
what is bulk flow
movement of protein free fluid between plasma and interstitial fluid
what does bulk flow occur through
water filled channels
what is the function of bulk flow
distribution of ECF volume NOT exchange of nutrients and metabolic products which occurs more rapidly via diffusion
what is filtration
plasma to ISF
what is absorption
ISF -> plasma
what are the pressures that govern bulk flow/starlings forces
-hydrostatic pressure of capillary
- colloid osmotic pressure in capillary
- colloid osmotic pressure of ISF
- hydrostatic pressure of ISF
what are the primary determinants that govern bulk flow
hydrostatic pressure of capillary and colloid osmotic pressure in capillary
what is hydrostatic pressure of capillary and numbers
force exerted by the fluid pressing against a capillary wall (capillary BP)
-30mmHg arterial end, 10mmHg venous end
what type of force is the hydrostatic pressure of capillary
filtration force
what is colloid osmotic pressure in capillary and number
osmotic force created by impermeable plasma proteins
-28 mmHg
what type of force is the colloid osmotic pressure in capillary
absorptive force
what is colloid osmotic pressure of ISF and number
force exerted by the impermeable proteins in the ISF
- 8mmHg
what type of force is the colloid osmotic pressure of ISF
filtration
what is hydrostatic pressure of the ISF and number
force exerted by the fluid in the ISF
=(-)3mmHg
what type of force is the hydrostatic pressure of ISF
absorptive force
what does net filtration pressure determine
the direction and magnitude of H2O movement via bulk flow
what is NFP impacted by
starlings forces
-capillary permeability
how do you calculate NFP using the starling equation
=Kf[(Pc + pi(if))-(pi(c)+Pif)]
what would a positive net value of NFP mean
net filtration
what would a positive net value of NFP mean
net filtration
what would a negative net value of NFP mean
net absorption
what is the NFP at the arterial end of the capillary? venous? across entire capillary?
arterial- 13 mmHg
venous: -7mmHg
across entire capillary: 6mmHg
what is the net filtration by systemic capillaries
2-3L per day
what does overall net filtration pressure vary based on
status of arterioles feeding capillary bed
what is the driving force for bulk flow
starlings forces
what is the determinant of resistance in bulk flow
capillary permeability
what are the functions of the lymphatic system
-return filtered fluid and proteins to circulation
-transporting absorbed fat from small intestine to circulation
- immune system
how much does the lymphatic system produce per day
3L filtrate
why do proteins need to be returned to circulation
injury to capillaries and hormones and paracrines can make the capillary leaky
what is the mechanism of lymph flow
-smooth muscle in the wall of lymphatics exerts a pumplike action
-lymphatic vessels have valves similar to those in veins
-skeletal muscle pump and thoracic pump
what are the causes of edema
-loss of normal lymph drainage
- loss of abnormal balance between starlings forces
what would cause loss of normal lymph drainage
-blocked by parasites
-removal/damage during surgery
what would cause loss of normal balance between starlings forces
-high Pc
-low pi C
-high pi IF
-high Kf
-reduced lymph drainage
what causes increases pi IF in edema
increased protein concentration in ISF, increased KF, and loss of normal lymph drainage
what causes increased P c in edema
arteriolar dilation
venous constriction
-increased venous pressure
-heart failure
-NOT INCREASED MAP
what causes decreased Pi C in edema
decreaed plasma protein concentration
-severe liver fialure
-protein malnutrition
-nephrotic syndrome
what causes increased KF in edema
burn
inflammation
what causes impaired lymphatic drainage in edema
standing
removal of lymph nodes
infection of lymph nodes
what is the tx for edema
ice elevation and compression
how does ice help edema
decreased temperature decreases movement of filtration and causes vasoconstriction
how does elevation help edema
gravity
how does compression help edema
artificially inflates hydrostatic pressure in isf and decreases filtration out