Ch. 18 Hemodynamics

Question 1

__________________________________ is the study of blood moving through the circulatory system.

Answer 1

Hemodynamics is the study of blood moving through the circulatory system

Question 2

______________, also called volume flow rate, indicates the volume of blood moving during a particular time.

Answer 2

Flow, also called flow rate, indicates the volume of blood moving during a particular time.

Question 3

Units for flow:

Answer 3

volume/ time

Question 4

_______________________ indicates the speed or swiftness of a fluid moving from one location to another.

Answer 4

Velocity indicates the speed or swiftness of a fluid moving from one location to another

Question 5

Units for velocity:

Answer 5

distance/ time

Question 6

what are the 3 basic forms of bloodflow?

Answer 6

1. pulsatile
2. phasic
3. steady

Question 7

________________________ flow is when blood accelerates and decelerates as a result of cardiac contraction; therefore this flow appears in the arterial circulation.

Answer 7

Pulsatile flow is when blood accelerates and decelerates as a result of cardiac contraction; therefore this flow appears in the arterial circulation

Question 8

________________________ flow also occurs when blood accelerates and decelerates as a result of respiration; appears in the venous circulation.

Answer 8

Phasic flow also occurs when blood accelerates and decelerates as a result of respiration; appears in the venous circulation

Question 9

______________________ flow occurs when a fluid moves at a constant speed or velocity.

Answer 9

Steady flow occurs when a fluid moves at a constant speed or velocity.

Question 10

____________________ flow is when the flow streamlines are aligned and parallel (normal physiologic states)

Answer 10

Laminar flow is when the flow streamlines are aligned and parallel (normal physiologic states)

Question 11

What are the 2 forms of Laminar flow?

Answer 11

1. Plug Flow
2. Parabolic Flow

Question 12

_______________ flow occurs when all of the layers and blood cells travel at the same velocity.

Answer 12

Plug flow occurs when all of the layers and blood cells travel at the same velocity.

Question 13

________________ flow has a bullet-shaped profile. Velocity is highest in the center of the lumen, and gradually decreases to its minimum at the vessel wall.

Answer 13

Parabolic flow has a bullet-shaped profile. Velocity is highest in the center of the lumen, and gradually decreases to its minimum at the vessel wall.

Question 14

The _____________________________ predicts whether flow is laminar or turbulent.

Answer 14

The Reynolds number predicts whether flow is laminar or turbulent

Question 15

The Reynolds number for laminar flow is less than _________________

Answer 15

The Reynolds number for laminar flow is less than 1,500

Question 16

____________________ flow is characterized by chaotic flow patterns in many different directions and at many speeds.

Answer 16

Turbulent flow is characterized by chaotic flow patterns in many different directions and at many speeds

Question 17

Turbulence is often associated with cardiovascular ______________________ and elevated blood ______________________

Answer 17

Turbulence is often associated with cardiovascular pathology and elevated blood velocities

Question 18

sound associated with turbulence is called a _________________ or _____________________

Answer 18

sound associated with turbulence is called a murmur or bruit

Question 19

Tissue vibration associated with turbulence is called a _____________

Answer 19

Tissue vibration associated with turbulence is called a thrill

Question 20

The Reynolds number for turbulent flow is greater than ________________

Answer 20

The Reynolds number for turbulent flow is greater than 2,000

Question 21

When blood moves from regions of higher energy to lower energy this is called __________________________ (pressure difference)

Answer 21

When blood moves from regions of higher energy to lower energy this is called energy gradient (pressure difference)

Question 22

What are the 3 energy forms associated with blood?

Answer 22

1. kinetic energy
2. pressure or potential energy
3. gravitational energy

Question 23

_______________________ energy is the ability of blood to do work as a result of its velocity. Associated with a moving object

Answer 23

Kinetic energy is the ability of blood to do work as a result of its velocity

Question 24

Kinetic energy is determined by two factors:
an objects _______________ and the ______________ at which it moves

Answer 24

Kinectic energy is determined by

an objects mass and the speed at which it moves

Question 25

____________________ or ________________________ energy is pressure force energy, it is the main form of energy found in flowing blood

Answer 25

*Pressure Energy* or *Potential Energy* is pressure force energy, it is the main form of energy found in *flowing blood*_____

Question 26

How does pressure create blood flow?

Answer 26

by overcoming resistance

Question 27

_________________________ energy is the ability to do work as a result of gravity, it is a form of stored or potential energy.

Answer 27

*Gravitational Energy* is the ability to do work as a result of gravity, it is a form of stored or potential energy

Question 28

As blood flows through the circulation, energy is lost in 3 ways:

Answer 28

1. viscous loss 2. friction loss 3. inertial loss

Question 29

_______________________describes the thickness of a fluid; so __________________ energy loss is associated with blood overcoming its internal stickiness.

Answer 29

*Viscosity* describes the thickness of a fluid; so *viscous energy loss* is associated with blood overcoming its internal stickiness

Question 30

Viscous energy loss in blood is determined by ___________________________

Answer 30

Viscous energy loss in blood is determined by *hematocrit*

Question 31

What is the normal average hematocrit?

Answer 31

45%

Question 32

_________________________ energy loss occurs when flow energy is converted to heat as one object rubs against another.

Answer 32

*Frictional energy loss* occurs when flow energy is converted to heat as one object rubs against another

Question 33

____________________ energy loss is the tendency of blood to resist changes in velocity

Answer 33

*Inertial energy loss* is the tendency of blood to resist changes in velocity

Question 34

When does Inertial energy loss occur?

Answer 34

1. pulsatile flow 2. phasic flow 3. velocity changes at a stenosis

Question 35

Velocity is ___________________ when the vessel narrows, and ___________________ when the vessel widens

Answer 35

Velocity is *greater* when the vessel narrows, and *weaker* when the vessel widens

Question 36

______________________is the narrowing in the lumen of a vessel

Answer 36

*stenosis* is the narrowing in the lumen of a vessel

Question 37

What are the effects of a stenosis?

Answer 37

change in flow direction increased velocity as vessel narrows tubulence downstream form the stenosis pressure gradient across the stenosis loss of pulsatility

Question 38

__________________________________ states that generally as a vessel narrows flow velocity increases and pressure simultaneously decreases. Pressure energy is converted into kinetic energy.

Answer 38

*Bernoulli's Principle* states that generally as a vessel narrows flow velocity increases and pressure simultaneously decreases. Pressure energy is converted into kinetic energy.

Question 39

pressure gradient =

Answer 39

flow x resistance

Question 40

voltage =

Answer 40

current x resistance

Question 41

How does Ohms law relate to pressure gradient?

Answer 41

pressure gradient is analogous to voltage; flow is analogous to current; resistance is the same

Question 42

Electrical resistance is reported in units of:

Answer 42

Ohms

Question 43

What are the circulatory system's resistance vessels?

Answer 43

arterioles

Question 44

What are the main characteristics of veins?

Answer 44

Thin-walled and collapsible, low resistance vessels

Question 45

Describe veins during normal function

Answer 45

low pressure, partially filled with blood, partially expanded (flattened hourglass shape)

Question 46

Venous inflow

Answer 46

hourglass cross sectional shape changes to oval then to round. This allows veins to accommodate a large volume increase with a very small increase in pressure. Once veins empty out they return to their original hourglass shape

Question 47

Why do veins expand during inflow?

Answer 47

This allows a high volume of blood with only a small pressure increase; resistance decreases and outflow to heart increases

Question 48

_____________________________________ is pressure related to the weight of blood pressing on a vessel measured at a height above or below heart level.

Answer 48

*Hydrostatic Pressure* is pressure related to the weight of blood pressing on a vessel measured at a height above or below heart level.

Question 49

When supine, hydrostatic pressure is

Answer 49

zero everywhere

Question 50

below the heart the hydrostatic pressure is

Answer 50

positive, resulting in a measurement that is too high

Question 51

above the heart, hydrostatic pressure is

Answer 51

negative, resulting in a measurement that is too low

Question 52

At the heart, the hydrostatic pressure is

Answer 52

zero, the move accurate measurement

Question 53

How does respiration have an effect on the venous system?

Answer 53

1. the venous system is low pressure 2. muscles responsible for respiration alter pressures in the thorax and abdomen

Question 54

What 2 venous flows does breathing affect?

Answer 54

1. venous flow in the legs 2. venous return to the heart which compromises venous flow from the head, arms, and IVC to the heart

Question 55

With Inspiration: Diaphragm moves _______________________ toward the abdomen Thoracic pressure _________________________ Abdominal pressure ____________________________ Venous return to the heart ________________________ Venous flow in legs ___________________________

Answer 55

With Inspiration: Diaphragm moves *downward* toward the abdomen Thoracic pressure *decreases* Abdominal pressure *increases* Venous return to the heart *increases* Venous flow in the legs *decreases*

Question 56

With Expiration: Diaphragm moves _________________________ into the thorax Thoracic pressure _________________________ Abdominal pressure __________________________ Venous return to the heart ______________________ Venous flow in legs ________________________

Answer 56

With Expiration: Diaphragm moves *upward* into the thorax Thoracic pressure *increases* Abdominal pressure *decreases* Venous return to the heart *decreases* Venous flow in the legs *increases*