| arterial pressure (Pa) is controlled by either 1_________ or 2____________ | 1. cardiac output control
2. local blood flow control (TPR) |
| cardiac output is controlled by the | sum of all tissue flows |
| the rate of blood flow to most tissues is dependent on | tissue needs |
| enumerate the physiology of hemodynamics (3) | 1. distensible tubes (blood vessels)
2. heterogenous fluid (blood)
3. pulsatile flow |
| formula for CO | CO = SV x HR (L/min) |
| veins and venules are known as _________ and they fxn as ________. why? | capacitance vessels
volume reservoir
because much of the BV will remain in the veins and venules |
| Amount of blood that passes a given point of circulation in a given period of time | flow |
| Distance travelled by the volume of blood given a period of time. | velocity |
| flow is identical to what hemodynamic parameter? | cardiac output |
| relationship between velocity and cross-sectional area | inversely proportional |
| As cross-sectional increases | the velocity decreases |
| velocity is ________ proportional to flow rate | directly proportional |
| which vascular segment will have the most rapid velocity of blood flow? | aorta (only 2.5 cm^2) |
| which vascular segment will have the SLOWEST velocity of blood flow? | capillaries (2500 cm^2) |
| the capillaries have large cs area and a slow velocity and this allows what? | - allows exchanges of diffusable substances between blood and tissues |
| velocity is _______ proportional to pressure | directly proportional |
| Hemodynamics is based on a fundamental law of physics: | OHM’s LAW |
| 2 main determinants of blood flow in the body | 1. pressure gradient
2. resistance |
| Flow is __________ proportional to your intravascular pressure gradient | directly (Q= deltaP / R) |
| Flow is _______ proportional to the resistance to flow | inversely |
| it is the change in pressure from inlet of the blood vessel and the outlet along a given length | pressure gradient (delta P) |
| is the impediment to blood flow exerted by the vessel wall and other physical factors | resistance |
| 2 Main Pressures that determine the movement of blood flow in the systemic circulation | 1. pressure inlet
2. pressure outlet |
| pressure inlet represents the | aortic pressure |
| The 1)_______ is the first segment of the systemic circulation that receives blood from the left ventricle under 2)_______ pressure | 1. aorta
2. high pressure |
| The average aortic pressure throughout 1 cardiac cycle | MAP |
| the pressure outlet is represented by the | central venous pressure (CVP) |
| CVP is a direct estimate of which type of pressure | RAP |
| is the sum of all resistances across all segments of the blood vessels in the systemic circulation | TPR |
| In most steady state conditions, blood flow in the body is | laminar |
| Blood is a heterogeneous fluid → flow in layers → layers are called | lamina
(see figure. blood flows in layers) |
| TRUE OR FALSE
Blood vessel walls exert resistance to blood flow mostly to the layer closest to it due to the rough surface of the vessel wall | true |
| what do you call the the force that is exerted by the blood vessel wall to the blood flow? | shear stress |
| the sight setting that will cause a projectile to hit the center of the target with no wind blowing | zero |
| the central portion of blood flow will be _______ because it is farthest from the vessel wall | fastest |
| Occurs when laminar flow is disrupted | turbulent flow |
| when the layer of blood crosses the midline, it creates | Eddy currents |
| Greater/lesser energy is needed to drive the volume of blood | greater |
| Whether a flow becomes turbulent or not, it is determined by the | Reynold’s Number (NR) |
| If NR is > 3000 = _________ BLOOD FLOW | turbulent blood flow |
| If NR less than _____ = laminar blood flow | less than 2000 |
| if NR is between 2000-3000 blood flow is | transitional |
| are variables that also determines the dynamic component of pressure based on Bernoulli’s equation | ? ??? ? (density and velocity) |
| increased Velocity of blood flow
increased Diameter of blood vessel
increased Density of blood (constant)
decreased Viscosity of blood
will increase/decrease NR? | increase |
| what happens to the NR when you decrease the diameter of the blood vessel? will it decrease NR as well? | no, since density and velocity (the Pdyn in Bernoulli's eq'n) are the same, it will not decrease the NR.
all the other variables must be constantly decreased or increased for the NR to be affacted |
| what happens to the NR of patients with severe anemia? | low hematocrit, low viscosity
= increased NR (turbulent blood flow) |
| in patients with severe anemia, an increased in velocity of blood flow associated with 1)___________ and 2)__________ which is a 3)__________ response to maintain O2 demand to tissues | 1. tachycardia (increased HR)
2. high CO
3. compensatory response |
| patients with severe anemia present with what type of murmur? | functional murmur (because of the turbulent flow accompanied by audible vibrations) |
| what is the common unit used for resistance? | PRU (peripheral resistance unit) |
| resistance is 1)_______ proportional to viscosity and length of tube and 2) _________ proportional to the vessel caliber (pie r^4) | 1. directly
2. inversely |
| interpret the graph below: | as the vessel dm becomes smaller (e.g., arterioles or venules), resistance increases
the larger the dm (ex. internal dm in aorta or veins and vena cava), there is lower resistance |
| it is the site of greatest resistance | arterioles |
| TRUE OR FALSE.
the capillaries, despite having the smallest internal dm is the site of greatest resistance | the capillaries, despite having the smallest internal dm is NOT the site of greatest resistance. the ARTERIOLES have the greatest resistance |
| why are the capillaries, despite having the smallest internal dm is NOT the site of greatest resistance? | - the capillary walls have no smooth muscles unlike arterioles
- parallel arrangement of capillaries |
| why do the arterioles have the greatest resistance? | - they have smooth muscles
- smooth muscles are innervated by autonomic nerves
- thus, they could constrict or dilate the arterioles |
| if the blood vessels are arranged in parallel to each other (e.g., capillaries), the total resistance of the unit would be _____ compared to individual vessel | less |
| if the arteriole is constricted and there is an increased resistance, the blood flow is | decreased
remember: resistance is the impediment to blood flow |
| it is the resistance of the ENTIRE systemic circulation
i.e., the sum of all resistances of the arteries, arterioles, capillaries, venules, and veins | Total peripheral resistance (TPR) |
| TPR increases/decreases by ____-fold | 4-fold |
| the principal determinant of resistance to blood flow through any vessel is the | caliber or dm of the vessel |
| Measure of blood flow through a vessel for a given pressure | conductance |
| conductance is ______ to resistance | reciprocal |
| there will be greater conductance of blood flow in areas where there is _______ resistance | least |
| Conductance is directly proportional to the ____ power of the vessel diameter | 4th powerthe conductance of blood flow dramatically changes proportional to the 4th power of the vessel diameter |
| exerts internal friction against the vascular wall and adjacent cells thus, contributing to the resistance of blood flow | blood viscosity |
| blood viscosity is measured in terms of | hematocrit |
| blood viscosity is mainly due to the | RBCs suspended in the blood |
| If hematocrit level is high then the blood viscosity is increased/decreased? | increased |
| can plasma protein concentration affect viscosity? | yes, but not significant |
| Based on Poiseuille equation, the greater the viscosity, the ____ the FLOW in a vessel if all other factors are constant | less flow |
| Based on Poiseuille equation, the greater the viscosity, the ____ the RESISTANCE in a vessel if all other factors are constant | higher resistance |
| In the body under physiologic conditions, the viscosity is _________ | constant |
| the most critical determinant of flow and resistance is ______________ represented by __________- | vessel diameter
radius to the 4th power |
| is the difference of pressure in the internal/intravascular space and outside the vascular wall | transmural pressure |
| according to the law of Laplace:
Wall tension for thin-walled tubes similar to blood vessels, is ___________ to the transmural pressure gradient times the radius of tube (blood vessel) and the wall thickness | proportional |
| The larger the vessel radius, the__________ the wall tension required to withstand internal pressure.
what is this law? | LARGER
law of Laplace |
| why is the aorta more prone to rupture? | Aorta is more prone to rupture as it requires higher wall tension due to its large internal dm |
| In the capillaries with small internal diameter, small radius, and even thinner wall compared to aorta,________ transmural gradient is required to withstand the internal pressure | LOWER |
