Lecture 4

Question 1

how does blood flow?

Answer 1

from high to low pressures

Question 2

a difference in pressure gradients causes what?

Answer 2

blood flow

the greater the difference the more flow

Question 3

what is cardiac output?

Answer 3

amount of blood entering the arteries per minute. Increased volume increases blood pressure.

normal: 5L/min

Question 4

what is peripheral resistance

Answer 4

amount of blood in the arterial circulation. If the peripheral resistance increases, the amount of blood in the arteries increases.

Question 5

how does the diameter of arterioles effect peripheral resistance

Answer 5

higher peripheral resistance in the constricted state.

There is a decrease in peripheral resistance in the dilated state.

Question 6

viscosity of blood

Answer 6

increase viscosity increases resistancee

Question 7

poiseuilles law

Answer 7

Q= volume flow
p1-p2= pressure gradient 
r=radius to 4th power 
L=length of tube 
V=viscosity

Question 8

What happens if you increase the Pressure Gradient and the Radius
remains the same?

Answer 8

The Greater the Pressure Gradient the Greater the Flow

Question 9

what happens to the volume flow in a hemodynamically

significant stenosis?

Answer 9

Velocities increase at the site of the stenosis, X. The volume flow should remain the same because of the increased pressure gradient.

Question 10

pulsatile flow

Answer 10

arterial flow

flow and velocities change during the cardaic cycle

Question 11

laminar flow

Answer 11

Arterial flow travels in laminar fashion in the arteries. It travels in concentric layers with the fastest flow in the center stream
The slowest flow along the wall is the boundary layer.

Question 12

what is this image of?

Answer 12

Disturbed flow (spectral broadening) profile due to plaque

Question 13

what is this image of?

Answer 13

Increased flow velocities due to stenosis. Spectral broadening also is present.

Question 14

total fluid energy equation

Answer 14

PE + KE + energy losses

Question 15

potential energy

Answer 15

blood pressure

Question 16

kinetic energy

Answer 16

blood flow

Question 17

energy loss

Answer 17

heat

Question 18

viscous losses

Answer 18

friction between the formed elements of the blood. Effected by the diameter of the lumen.

Question 19

Inertial losses

Answer 19

due to acceleration and deceleration of the pulsatile flow and direction changes.

Question 20

bernoullis equation

Answer 20

Q= volume flow 
V= velocity 
A= area of tube

Question 21

what does bernoullis principle describe?

Answer 21

Describes the pressure drop that occurs in a stenosis.

The higher the velocity, the lower the pressure.

Question 22

what is the energy gradient through a stenosis

Answer 22

decrease in potential energy
increase in kinetic energy
energy loss due to heat

Question 23

As the diameter reduction of an arterial stenosis increases…

Answer 23

the pressure gradient increases.

Question 24

50% to 70% stenosis

Answer 24

Volume flow remains the same as the velocities increase.

Question 25

70 % or more stenosis

Answer 25

Increased velocities no longer compensate for the volume flow. This is a hemodynamically significant stenosis.

Question 26

pre stenotic spectral

Answer 26

Question 27

post stenotic spectral

Answer 27

Question 28

distal to stenosis spectral

Answer 28

As flow exits a stenosis, the velocities decrease and bi-directional flow occurs due to boundary layer separation. tardus parvus

Question 29

spectral at the site of the stenosis

Answer 29

Increase in peak systolic velocity (psv), end diastolic velocity (edv)

Question 30

the greater the stenosis what happens in end diastole

Answer 30

decreases | increase in resistance to flow depending upon grade of stenosis

Question 31

what is the boundary layer

Answer 31

is the slowest blood flow along the wall of the artery is separates from the wall of the artery sudden decrease in diameter

Question 32

what are the inertial loss due to stenosis

Answer 32

direction change as flow direction narrows and broadens | turbulence at the entrance and exit

Question 33

what causes the increase to resistance to flow

Answer 33

* Stenosis * Surface roughness * Curvature and tortuosity of the vessel * Noncircular vessel cross section * Vortices, eddies, reversal of flow (turbulence)

Question 34

what type of flow do you see in the carotid bulb?

Answer 34

flow reversal

Question 35

how can you tell the difference between the ICA and ECA

Answer 35

the ICA has a larger proximal diameter after bifurcation

Question 36

how is the flow around a curve in a vessel?

Answer 36

tuburlent