Exam 3 Kirk Lecture 1 : Hemodynamics 1 Flashcards
What is the function of the venous system? Is it low or high pressure? Type of valves?
What is the function of the lymphatic system?
What is the function of the arterial system? Low or high pressure?
Venous system: low pressure, controls volume (has veins, low resistance vessels, uni directional valves, right heart)
Lymphatic System: drainage
Arterial System: high pressure, controls pressure, left heart
Function of the capillaries
Capillaries: network exchange vessels, O2 and nutrients to tissues and organs
Explain the function of the following:
Left Heart
Elastic arteries
Muscular arteries
Arterioles
Capillary network
Left heart: pressure pump, delivers blood to elastic arteries
Elastic arteries: serve as surge pump in which energy is stored during systole and released during diastole… positive pressure in aorta ensyres flow in capillaries during cardiac cycle (120/80 mmHg)
Muscular arteries: serve as low resistance conduits that deliver blood quickly to tissues with minimal energy expenditure
Arterioles: variable resistors, change diameter and regulate the blood flow into the capillaries
Capillary network: exchange vessels deliver O2 to target organs
Explain the function of the following:
Venous vessels
Right heart
Pulmonary vessels
Lymphatic vessels
Blood
Venous vessels: capitance vessles, variable capacitors, change the volume of the vascular system to match the volume blood needed, one way valves
Right heart: serves as volume pump, delivers large volumes of blood to the pulmonary circulation at low pressure
Pulmonary vessels: gas exchange and volume reservoir
Lymphatic vessels: drainage system, returns fluids to bloodstream
Blood: carries nutrients, signaling molecules
Describe the three types of pressure in the circulatory system:
Hydrostatic Pressure
Driving Pressure
Transmural Pressure
Hydrostatic Pressure: pressure from gravity (example: why you get dizy when you stand up from couch)
Driving pressure: pressure driving blood flow (high to low)
Transmural pressure: pressure of fluid pushing on a wall (what is normally measured as blood pressure)
The circulatory system maintains constant blood flow
Define the velocity of blood flow
Define “flow rate”
Does flow increase or decrease with cross sectional area
Velocity of blood flow: distance that a particle travels with respect to time, cm/sec
Flow Rate: volume of blood moving per unit time
Flow Rate: v = Q/A
or
velocity = flow rate / cross sectional area
Flow is slower over a wider sectional area (think putting your hand over a water hose spout
Bernoulli’s Principle:
In a ________, the total energy (____ + _____+ ____) remains constant.
What is the equation?
In a constant flow system, the total energy (potential, kinetic, gravitational) remains constant
Bernoulli’s Equation:
In stenosis: ______ increases and _____ decreases
Thus, transmural pressure _______ as the velocity of the blood flow increases in the stenotic region
In stenosis (an abrupt decrease in vessel cross-sectional area), kinetic energy/flow increases, while potential energy decreases.
Thus, transmural pressure decreases as the velocity of blood flow increases in the stenotic region.
Therefore, there is less pressure pushing against eh stenotic region, making it even worse.
In stenotic regions, blood flow technically does what?
What is a better way to think about blood flow
In stenotic regions, the pressure in the stenotic region is lower than in a downstream segment. Therefore, blood in that case is moving from low to high pressure.
THUS, it is more correct to understand that blood flow moves from higher to lower TOTAL energy.
Total energy made up of potential and kinetic.
Total energy in stenotic region is higher because of how much higher the kinetic energy is.
Blood flow moves from what to what
Blood flows from high total energy to lower total energy
Also, friction causes a loss of total energy as blood flows through the vessels
Explain blood pressure measurements at the ascending aorta: side port catheter vs end port catheter measurements
There are two catheters: a side port (measures PE)
and a end port (measures KE + PE)
If a cathetor has an end port sensor that is facing the flowing stream of blood, it will measure a pressure that is higher than the pressure measured by the side port sensor on the same cathetor.
Side port measures only potential energy - therefore is more accurate
What is Poiseuille’s Law?
It is analogous to ohm’s law
Equation: Q = deltaP/ R (DeltaP = QR)
Pressure = flow x resistance
Poiseuille’s Law:
Blood flow is ______ to pressure gradient
Blood flow is ______ to vessel radius to 4th power
Blood flow is ______ to vessel length and blood viscosity
Resistance is _____ to vessel length and viscosity
Resistance is _____ to vessel radius to 4th power
Blood flow: directly proportional to pressure gradient and radius to the 4th…. inversely proportional to vessel length and blood viscosity
Resistance is directly proportional to vessel length and blood viscosity
Resistance is inversely proportional to vessel radius to 4th power
The most important determinants of blood flow are the ______ and the ______
Most important determinants of blood flow in the CV system are pressure gradient and the radius to the 4th power…………… pressure gradients are generally held constant by feedback mechanisms
Relationship between blood flow and radius
(what happens when radius doubles?)
Blood flow = radius ^ 4
So if blood flow doubles, radius increases x 16
What in the CV system are in series with each other?
Explain resistances in series
The aorta, large and small arteries, arterioles, capillaries, venules, veins, vena cava are all in series
Rt = R1 + R2+ R3
For resistances in series, the total resistance of the entire system equals the sum of the individual resistances
Therefore, each resistance is less than the entire system
Where is the primary site of arterial resistance?
Arterioles are the primary site of arterial resistance
What in the CV system is arranged in parallel?
Explain the resistances in parallel
Organs and vessels within a category of vessels (capillaries, etc) are arranged in parallel
For resistances in parallel, the total resistance is less than any individual resistance
1/Rt = (1/R1)+ (1/R2)+ etc
________ indicates the propensity for turbulent blood flow
The higher the _____ the greater change for turbulent blood flow to develop
Eqn:
Reynold’s number indivates the propensity for turbulent blood flow
Higher the Nr, the greater change for turbulent flood flow to develop
Eqn: Nr = (density)(diameter)(velocity) / (viscosity)
What would increase Reynold’s number vs decrease it
Increase Nr : density, velocity, tube diamter
Decrease Nr = viscosity
Explain the difference between laminar and turbulent blood flow
The larger the diameter, the ____ the chance to develop turbulent flow
Laminar Flow: fluid moves in parallel layers within tube (laminar is silent)
Turbulent/ non linear flow: disorderly pattern, results in : murmurs/bruits, damage to endothelial lining, thrombi, Korokoff sounds
The LARGER the diameter, the higher change to develop turbulent flor (aorta)
A person who has anemia has an ________
Aka where could you hear a bruit in someone with anemia
Person with anemia : check for bruit in aorta
Anemia: lower than normal RBCs in blood, hemtacrit is lower than normal, viscosity is lower, so renoyld’s number goes UP
Define the following terms in how they relate to viscosity:
Shear stress
Shear rate
Viscosity =
Shear stress : resistance to movement between layers aka pressure
Shear rate: relative velocities between layers (velocity of blood flow)
Viscosity = shear stress / shear rate
THEREFORE, viscosity = pressure over velocity
so velocity is equal to pressure/viscosity
Explain viscosity in a newtonian vs nonnewtonian fluid
As velocity of blood flow increases, viscosity _____ due to less interactions between components
Newtonian fluid: fluid whose viscosity remains constant (water or plasma)
Non-newtonian fluid: fluid whose viscosity changes
As velocity of blood flow increases, viscosity decreases due to less interactions between components
What is the normal range of hematocrit?
Normal range of hematocrit : 35-50%
Define Axial streaming and plasma skimming
As you go from the aorta down, hematocrit _____
As blood flow slows down from larger to smaller vessels, the viscosity should increase, but it DOES NOT because of ______
Axial Streaming: tendency for RBCs to cluster in axial/innermost and fastest layer, which creates a large cell free area around the outside, thus in smaller vessels they have a larger cell free area and thus a lower viscosity
Plasma skimming: tendency of smaller vessels to contain more plasma and less RBCs due to axial streaming (branching off effect)
Hematacrit is lower in smaller vessels due to plasma skimming
As blood slows down from larger to smaller vessels, the viscosity should increase, but it doesn’t in small vessles because of axial streaming and plasma skimming offset the shear thinning fluid effect of blood (they offset the slow velocity)
Capallaries can withstand incredibly high pressures without bursing.
What is the Laplace Equation that explains tension in a vessel wall
Tension = (pressure x radius)/ wall thickness
Or wall tension is directly related to pressure and radius, inversely related to wall thickness
Explain the following physiological concequences of Laplace:
Capallaries with a small radius can withstand _____
Laplace:
Capallaries with small radius can withstand very large transmural pressures
Explain the following due to the laplace relationship:
Arteriolar Vasoconstriction will ____ wall tension and provide _____
Arteriolar vasoconstriction will decrease wall tension and provide greater control over blood flow
(think, constrict means smaller radius, smaller radius means less tension)
Explain the following due to the Laplace equation:
Aneurysms result in a section of a vessel with a _____ radius, increasing the wall tension and creating a higher risk of bursting
Aneursyms result in a section of a vessel with a large radius, which will increase the wall tension and be at risk of bursing
Explain this using the laplace equation:
Dilated hearts have a larger radius and ______ wall tension and thus require more _________ to overcome
Dilated hearts have a larger radius and higher wall tension, thus requiring more systolic work and higher oxygen consumption to overcome
What is the equation for the laplace relationship aka the equation to calculate wall tension
T = P x radius / wall thickness
aka wall tension = [(pressure)(radius)]/ wall tension
