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69 Cards in this Set
- Front
- Back
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capacitance
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measure of the aility o hold a change in volume per change in time
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resistance formula
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R= 8Ln/rto the 4th(3.14)
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hydrostatic pressure
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p=mgh
p=hydrostatic pressure m=density of the fluid g=force of gravity h=height of the column |
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what is the formula for poiseuille's lae?
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Q=(3.14)(changeP)(r4)/8Ln
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explain bernoulli's equation?
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-energy is conserved
-pressure againsted a vessel wall is potential energy -kinetic energy is related to the velocity of fluid flow |
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what is bernoulii's equation?
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(changeP=4(v22'v12))
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what parameters increase the amount of energy lost to heat
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-smaller cross sectional area
-rougher surface -increased velocity -higher viscosity |
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what does a non-newtonian fluid mean?
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the viscosity of the blood changes the flow geometry, not just temperature
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going from LV to arterioles, what happens to capacitances and resistance?
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capacitance decreases, and resistance increases
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at rest, how much of the blood is contained in the venous system?
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65%
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velocity?
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it decreases
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how many mmHg are there per 5 cm?
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4 mmHg
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where is pressure the highest?
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in the heart, and gradually decreases as it moves distally
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what are the effects of viscocity on flow?
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Viscocity is the friction btw layers of fluid or a structure.
-the higher the viscocity, the higher the resistance to flow -viscocity is related to hematocrit; the higher the hematocrit, the higher the blood viscosity |
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what is friction, and what are its effects on flow?
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friction is the resistance of movement of one layer of blood against another layer or the vessel wall.
-velocity of blood cells is higher in the center of a vessel due to frictuion, viscoscity, and the laminar effect. -smaller vessel=more friction, and less flow |
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what determines how much blood enters the patient's arterial system?
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the heart
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what do arterials do
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determine the organ and tissue blood needs and control this through constriction and dialation of the arterioles.
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microcirculation
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blood flow from arterials to venules
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what determiens the amount of blood that enters and leaves the venous system?
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microcirculation
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how are high arterial pressures maintined within the body?
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through medium and large arteries
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where is the largest potion of blood volume at rest?
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in systemic veins and venules
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what is the main form of energy present in flowing blood?
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potential
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what are the types of potential energy in he blood system?
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-arterial wall elasticity
-intravascular pressure -hydrostatic pressure -gravitational potential energy |
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what does bernoulli's equation describe
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constant energy of fluid flow through a steosis
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what are the limitations of bernoulii's equation?
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-assumes that the points where flow is measured lie on a streamline
-assumes that flow has a constant density -assumes that there is no friction |
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bernoulli's equation is also known as:
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conservation of energy theorum
continuity rule |
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how are pressure and velocity related?
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inversly
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as flow goes up, what happens to pressure and diameter?
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pressure goes doen, and diameter is reduced
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T/F energy must be constant before and after a stenosis?
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true
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inertia
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resistance a mass encounters when acceleration (poise)
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what is the formula for flow?
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Q=(velocity)(x-sectional area)
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HOW DOES THE CONTINUIT EQUATIOION and the flow formula relate to blood flow int he blody?
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all the flow through one region must equal the flow in another
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using thoery learned about laminar flow, explain why blood flow velocity is slower in small vessels?
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-friction is creased btw each layer of flow and firction is greater along the walls
-in small vessels, layers in the middle are closer to the walls, and are delayed due to friction. |
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explain how poiseulle's law, which addresses viscous energy losses, relates to flow in a stenotic segment?
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-energy is lost from before a stenosis to after it
-energy loss is related to velocity in stenosis, length of the stenosis, and viscosity through stenosis -the tighter the stenosis, the more layers of blood have to be broken down(viscosity); so increased viscosity=increased resistance -small diameter changes=large rresistance changes |
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why do we not have laminar flow in our circulatory system?
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-flow velocity changes throughout the cycle
-change in vessel dimention and diameter -distorted lines of flow |
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what is turbulent flow directly proportional to? inversly?
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directly:
-diameter of blood vessel -viscocity of blood flow -density of blood inversly=viscosity of blood |
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what is reynalds number?
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an equation that measures the tenency for tubulence to occur.Number is small than 2000 in real life due to body movements, pulsatile flow, and roughness of intima
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what is the windkessel effect?
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-when fluid is forced into a complieant vessel causing it to expand and increase the volume within it. Later, when pressure is reduced, vessel contracts, producing extended flow.
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what does the windkessel effect cause in blood flow?
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continuted flow in diastole.
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as the diameter of a vessel increases, what happens to resistance?
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it decreases
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relate vasoconstriction to vessel lumen, resistance, and blood pressure
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as vasoconstriction occurs, the vessel lumen narrows causing arterioles to constrict, and resistance to increase which results in an increase in BP.
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relate viscocity to resistance and blood pressure?
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as viscosity increases, resistance and blood pressure increase
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where(in the circulatory system) is the greatest pressure droP?
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at the arteriole level where resistance to blood flow increases
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what factors control peripheral resistance?
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-sympathetic nerve regulation
-augtoregulation |
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explain how the heart, kidneys, cellular lining of blood vessels, and baroreceptors regulate blood pressure in the body?
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heart: via cardiac output
kidneys: regulates volume of fluid in blood vessels internal cellular lining: regulates local release of hormones Baroreceptors:movement to movement adjustments adjusted by postural changes |
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what is mean arterial pressure
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average blood pressure int the arteries
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pulse pressure
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systolic pressure-diastolic pressure
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cardiac pressure wave
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pressure changes from cardiac activity
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arterial pressure wave
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waves that result from the pulsatile variations in blood volume and enerty occuring with each cardiac cycle
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what factors affect the arterial pressure wave?
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-stroke volume
-time course of ventricular ejection -peripheral resistance -compliance or stiffness of arterial walls |
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what is critical stenosis
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narrowing of tha rterial lumen resulting in a hymodynamiclaly significant reduction in volume, pressure or flow(50-75%?
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what is the hydrostatic pressure at in the body when a person is lying down?
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hydrostatic pressure goes to 0
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how does respiration effect venous return?
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INSPIRATION:
-increase abdominal pressure -decreased thoracic pressure -increased venous return from abdomen to RA -decreased blood returen from legs to abdomen EXPIRATION: -decreased pressure in the abdomen, and increased thoracic pressure -decreased venous returm from the abdomen to RA -increased blood return from legs to abdomen |
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transmural pressure
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measure of pressure difference from within the vessel to pressure outside the vessel
-higher transmural pressure results in distended vein |
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if there is a diameter reduction within a vessel, what happens to flow and pressure?
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pressure drop w/flow increase
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what does higher velocities mean in regards to kinetic energy, and energy losses due to friction and viscocity?
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higher velocities imply greater kinetic energy, and greater energy losses due to friction and viscocity
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how does the length of the vessel, and viscocity of blood affect resistance?
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causes it to increase with a longer vessel and greater viscocity
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how is resisitance related to the diameter of a vessel?
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inversely proportional
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what 2 factors control perpheral vascular resistance?
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-sympatheic nerve innervations
-autoregulation |
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what is autoregulation?
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ability of mmost vascular beds to constrict in response to a rise in blood pressre and dialate in response to a fall
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when can a person's ablity to autoregulate go away?
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when perforation pressure falls below a critical level(severe atherosclerosis)
-vessels remain fully dialated |
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pressure
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-force exerted by the blood against a vessel wall
-force per unit area |
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as pressure increases, what happens to resistance in a vessel?
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as pressure increase, force increases which causes the vessel wall to expand, and in turn, there is lower resistance.
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flow; name 2 flow formulas
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-measure of volume per unit time
-flow=velocity x cross-sectional time -flow=change in pressure/resistance |
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as pressure difference and flow resistance increases, what happens to the flow rate, and volume flow rate respectively?
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-as pressure differences increases, flow rate increases
-as flow resistance increases, volume flow rate decreases. |
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how much blood is pumped each beat?
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70 ml
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as a pressure wave propegates through the arterial system, what happens to the mean and systolic pressures? why?
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systolic pressures increase due to increased stiffness of the vessel wall toward the periphery, and relfected waves
-mean pressure decreases due to losses in totatl fluid energy |
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what are the 2 periods of increased venous flow durind each cardiac cycle?
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-at ventricular systole(v-wave)
-after AV valves open(after c-wave) |
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what are the 3 positive pressure waves of the pressure curve?
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a-wave-atrial contraction and relaxation
c-wave-isovolumetric contraction v-wave-ventricular systole |
