Circulatory 1

Question 1

Poiseuille’s law

Answer 1

Steady laminar flow of Newtonian fluids through uniform cylindrical tubes

Question 2

Poiseuille’s law is analogous to . . .

Answer 2

Ohm’s law

Question 3

Equation for Poiseuille’s law

Answer 3

Force = change in pressure / resistance

Question 4

Flow is directly proportional to . . .

Answer 4

Radius to the fourth and pressure difference

Question 5

Flow is inversly proportional to . . .

Answer 5

length and viscosity

Question 6

Resistance is directly proportional to . . .

Answer 6

length and viscosity

Question 7

Resistance is inversely proportional to . . .

Answer 7

radius to the fourth power

Question 8

Most important determinants of blood flow in the CV system

Answer 8

Pressure gradient and the radius to the fourth power

Question 9

Viscosity

Answer 9

“Lack of slipperness”

Question 10

Shear stress

Answer 10

Resistance to movement between laminae

Question 11

Shear rate

Answer 11

Relative velocities between laminae

Question 12

Viscosity equation

Answer 12

Shear stress divided by shear rate

Pressure over velocity

Question 13

Newtonian fluid

Answer 13

A fluid whose viscosity remains constant over a range of shear rates and shear stress

Question 14

Non-Newtonian fluid

Answer 14

A fluid whose viscosity changes over a range of shear rates and shear stress

Question 15

Relationship between viscosity and hematocrit

Answer 15

As hematocrit increases, the viscosity increases (hyperbolic relationship: concave upward)

Question 16

Axial streaming

Answer 16

Tendency of red blood cells to accumulate in the axial laminae

Question 17

Plasma skimming

Answer 17

Tendency of smaller vessels to contain relatively more plasma and less red blood cells due to axial streaming

Question 18

Laminar flow

Answer 18

Fluid moves in parallel concentric layers within a tube

Question 19

Turbulent flow

Answer 19

Disorderly pattern of fluid movement. Non-laminar

Question 20

What sounds can turbulent flow cause/ what can they be a cause of?

Answer 20

Murmurs, damage to endothelial lining, thrombi, and Korotkoff sounds

Question 21

Reynold’s number

Answer 21

Dimensionless number indicating propensity for turbulent blood flow

Question 22

Determinants of Reynold’s number

Answer 22

Tube diameter, velocity, density, and viscosity

Question 23

Bernoulli Principle

Answer 23

In a constant flow system, the total energy (potential + kinetic) remains constant

Question 24

Describe what happens when there is an abrupt decrease in vessel cross-sectional area

Answer 24

Potential energy is converted into kinetic energy. Transmural pressure decreases as the velocity of blood flow increases in a stenotic region

Question 25

Laplace relationship

Answer 25

wall tension is equal to the pressure multiplied by the wall thickness or radius

Question 26

Laplace relationship - capillaries

Answer 26

Small radius, low wall tension. Can withstand very large transmural pressures

Question 27

Arterial vasoconstriction - Laplace relationship

Answer 27

Relatively large wall thickness/lumen diameter ratio; low wall tension. Provides greater control of vessel diameter and blood flow

Question 28

Aneurysm: Laplace relationship

Answer 28

Lage radius and high wall tension; cannot withstand transmural pressures and therefore will eventually rupture

Question 29

Dilated heart: Laplace relationship

Answer 29

Large radius, high wall tension, higher afterload. More systolic work, higher oxygen consumption to overcome higher wall tension

Question 30

Do veins or arteries have a higher cross-sectional area?

Answer 30

Veins

Question 31

Percentage of blood in veins

Answer 31

60%

Question 32

Percentage of blood in arteries

Answer 32

18%