Hemodynamics Flashcards
What do veins function as in the circulatory system?
Capacitors
What do arteries function as in the circulatory system?
Resistors
Is the arteriole curve of pressure and volume elastic or inelastic?
Inelastic
Is the venous curve of pressure and volume elastic or inelastic?
Elastic
What layers does an artery have?
- endothelium
- Elastic tissue
- Smooth muscle
- Fibrous tissue
What layers do arterioles have?
Endothelium, and smooth muscle layer
What layers do capillaries have?
Endothelial layer
What layers do venules have?
Endothelium and fibrous tissue
What layers do veins have?
- endothelium
- Elastic tissue
- Smooth muscle
- Fibrous tissue
What is the function of the smooth muscle found in arterioles and venules?
Exert tension during active contraction
Why is it important for BP to decrease as it enters capillaries?
To prevent tissue damage
The rate of blood flow to an organ or tissue is related to what?
The needs of the organ or tissue
CO is controlled by what?
The sum of individual tissue needs
Arterial pressure regulation is (in/dependent) of local blood flow or cardiac output control?
Independent
What are the units of blood flow?
cm^3/sec
What are the units of blood velocity?
cm/sec
What are the two ways that arterial pressure is controlled?
Nervous reflexes
Hormones
What is ohm law for blood flow?
d(pressure) /R = Flow
What is Poiseuille’s law for rigid tubes?
Flow = dP(pi)r4 / 8(viscosity)(length)
How can you measure viscosity clinically?
taking hematocrit
What is anomalous viscosity?
As blood flow decreases, viscosity increases
How does blood usually flow? Where is it fastest, and slowest?
In a laminar way (fastest in the inner layer, slowest at the outer layer)
What is the effect of laminar flow (what is the shape that it makes)?
Causes a parabolic flow of blood
What type of front does turbulent blood flow have?
Squared
Why is turbulent flow inefficient?
Have to overcome the resistance to move blood
When do you induce turbulent flow?
When listening for Korotkoff sounds
Which heart sound is produced from turbulent blood flow?
S4
What is Renolds number?
Propensity of fluid to produce a turbulent flow
What is the equation for turbulent flow?
Re = 2(radius)(velocity)(ro) / (viscosity)
How does vessel flow compare to a rigid tube?
Has a exponential curve, as opposed to a linear one
How does no SNS stimulation of vessels compare to high SNA stimulation?
No SNS allows for higher flow rates at lower pressures
x^2 curve
How does SNS change resistance?
Increases it, which will decrease flow (1/x curve)
What is the transmural pressure equation?
Tension = (d pressure)(radius)
As vessel radius increases, or blood pressure increases, what happens to wall tension?
increases (Tension = (d pressure)(radius))
What is the buffer for changes in wall tension?
Elastic tissue in vessels
What happens to the blood flow as it goes through capillaries? Note that flow = (velocity)(CSA).
Flow remains constant. Thus velocity increases if CSA decreases, and vice versa
Does the capillary bed have an increase in CSA or decrease relative to arteries? What, then, happens to velocity?
Increased, thus velocity decreases
Is blood resistance lower or higher when vessels are run in a series?
Higher (R1 +R2)
Is blood resistance lower or higher when vessels are run in parallel?
Lower (1/R1 + 1/R2)
Review all the equations
Don’t press 5.
What is the critical closing pressure?
The point of pressure at which there is infinite resistance
