Chapter 2- Physiology And Hemodynamics

Question 1

Name the flow of blood starting from the heart

Answer 1

1) Left ventricle
2) Aorta
3) Large arteries
4) arterioles
5) capillaries
6) venules
7) Large veins
8) Vena cava
9) Right atrium

Question 2

Energy: Movement of any fluid medium between two points requires two things:

Answer 2

1) pathway along which fluid can flow

2) pressure differential ( high pressure moves to lower pressure)

Question 3

What does the amount of flow depend on?

Answer 3

1) energy difference

2) any resistance which tends to oppose such movement

Question 4

Grey box:

Lower resistance = higher flow rate
Higher resistance = Lower flow rate

Answer 4

.

Question 5

What is the major form of Energy for circulation of blood?

Answer 5

Pressure (potential/ stored energy)

Question 6

What is kinetic energy?

Answer 6

Velocity

• small for circulating blood
• expressed in terms of fluid density and velocity measurements

Question 7

What is Gravitational energy?

Answer 7

Hydrostatic pressure (HP)

Weight of the column of blood extending from the heart to level where pressure is measured

Question 8

An energy gradient is needed to move blood from one point to another. The _________ the gradient; the _________ the flow.

Answer 8

Larger; greater

Question 9

What is Inertia?

Answer 9

Related to tendency of a fluid to resist change in its velocity (example: body at rest stays in rest)

Question 10

Resistance if directly proportional to what?

Answer 10

Viscosity (thickness of blood) and length

Question 11

Resistance is inversely related to what?

Answer 11

Radius

Question 12

What has the most dramatic effect on resistance of a blood vessel?

Answer 12

Vessel diameter

Question 13

Elevated hematocrit does what to blood?

Answer 13

Increases blood viscosity ( thickness of blood)

Severe anemia: decreases blood viscosity

Question 14

Grey box:

Increase in viscosity = decrease in velocity

Decrease in viscosity = increase in velocity

Answer 14

.

Question 15

What is parabolic flow?

Answer 15

Higher frequency flow in center of vessel. Laminar flow considered stable flow

Question 16

Where is plug flow seen?

Answer 16

Vessel origin as well as during initial cardiac upstroke

Blunted flow

Question 17

What causes viscous energy loss?

Answer 17

Increased friction between molecules and layers which ultimately cause energy loss

Question 18

Where do inertial losses occur?

Answer 18

Deviations from laminar flow, due to direction and/or velocity changes

Example: exit of a stenosis

Question 19

What does the Poiseuille’s equation show relationships of?

Answer 19

Pressure, volume flow, resistance

Question 20

What is volume flow directly related to?

Answer 20

Pressure

Question 21

What is volume flow inversely related to?

Answer 21

Resistance

Question 22

What is the relationship between area and velocity?

Answer 22

Inversely related

• increase area ; decrease velocity
• decrease area ; increase velocity (ex: stenosis)

Question 23

What is the relationship between velocity energy and pressure energy?

Answer 23

Inversely related
- increase in velocity = decrease pressure

• decrease in velocity = increase in pressure

Question 24

What is boundary layer separation?

Answer 24

They occur because of chAnge with or without intra-luminal disease; and because of curves

Question 25

In presence of flow separation, what happens with the velocity and pressure?

Answer 25

Decrease in velocity; increase in pressure

Question 26

What is the Reynolds number when Laminar flow becomes disturbed?

Answer 26

> 2000 (unitless number) AKA Turbulent flow

Question 27

Looking at a triphasic waveform, what does the dicrotic notch tell us?

Answer 27

Related to closure of the aortic valve and the influence of peripheral resistance

Question 28

What are examples of arteries that have low resistive waveforms?

Answer 28

- ICA - vertebral - renal - celiac - splenic - hepatic ** main arteries that feed organs**

Question 29

What are some examples of low resistive arteries?

Answer 29

- ECA - subclavian - aorta - iliac - extremity arteries - fasting SMA

Question 30

What can happen to a normal high resistant signal as it approaches a significant stenosis or obstruction?

Answer 30

Become monophonic

Question 31

What does the diastole in a waveform reflect in low and high resistance?

Answer 31

Low resistance: higher diastole, continuous blood flow | High resistance: little to no diastole

Question 32

What is vasodilation?

Answer 32

Pulsatilla changes in medium/ small sized arteries of the limbs are decreased (lower resistant). When this occurs, pulsatility changes are increased in minute arteries

Question 33

Note: We inflow pressure falls due to stenosis; the usual response in periphery’s to maintain flow by vasodilation

Answer 33

.

Question 34

What is vasoconstriction?

Answer 34

Pulsating changes in medium/small sized arteries of the limbs are increased. When this occurs, pulsatility changes are usually decreased in the minute arteries.

Question 35

Know about collaterals?

Answer 35

1) location of the collaterals may help to determine tentative location of the stenosis/obstruction 2) arterial obstruction may alter flow in collateral channels nearby or further away from site of obstruction Changes include: elevated velocity, increase volume flow, pulsatility changes

Question 36

Know about effects of exercising?

Answer 36

1) causes peripheral vasodilation which lowers distal peripheral resistance, enhancing blood flow 2) Vasoconstriction and vasodilation of blood vessels within skeletal muscles are influenced by sympathetic nervous system for blood temperature 3) Exercise is a key vasodilator of resistance vessels within skeletal muscle

Question 37

What is auto regulation?

Answer 37

Ability of most vascular beds to maintain constant level of blood flow over a wide range of perfusion pressures

Question 38

When Blood pressure rises, what happens to the resistance vessels?

Answer 38

Constrict

Question 39

When blood pressure falls, what happens to resistance vessels?

Answer 39

Dilatation

Question 40

Box: Flow to a cool extremity (vasoconstriction) = pulsatile signals Flow to a warm extremity (vasodilatation) = continuous, signals

Answer 40

.

Question 41

Box: Pulsatility changes don’t differentiate well between occlusion and severe stenosis Waveforms may not be altered with good collateralization

Answer 41

.

Question 42

What are effects of a stenosis?

Answer 42

1) notable reduction in volume flow and pressure | 2) cross sectional area reduction of 75% = diameter reduction of 50%