Cardiac biophysics

Question 1

Blood is a _____ and ____ fluid

Answer 1

complex and incompressible

Question 2

Pressure is a ____ force always present

Answer 2

compressive

Question 3

Velocity is high in ____ vessels

Answer 3

large

Question 4

Increase in volume increases the stress on the walls of a vessel which increases the ____

Answer 4

pressure.

Question 5

Arterial pressure is _____ over the atmospheric pressure

Answer 5

120 mmHg

Question 6

Total blood coming into a system must be ___ to the total blood coming out

Answer 6

equal

Question 7

Flow rate (Q) formula

Answer 7

Q = Δ V / Δ t

Q = V x A

Question 8

How would we find the Q?

Answer 8

V1 x A1 = V3 [A3 x n3]

Question 9

When you increase the total cross sectional area what happens with velocity?

Answer 9

Velocity decreases

Question 10

What happens with Q if the radius within the same system changes (eg: stenosis)

Answer 10

Q = V x A

Smaller radius = Higher velocity, to compensate and keep Q constant.

Question 11

In a vertical tube with constant radius the velocity must be equal on the top and bottom. How is the Q maintain constant?

Answer 11

If kinetic energy is constant then the Q depends on the pressure and the potential energy.

(Bernoulli equation)

If potential energy is higher at the top then pressure must compensate, therefore pressure is greater on the bottom

Question 12

What does the Bernoulli equation represent ?

Answer 12

The mechanical energy in a fluid

Question 13

Bernoulli equation:

Answer 13

P + 1/2 ρ v2 + ρgh = cte in a fluid

1/2 ρ v2 = kinetic energy

ρgh = potential energy

Question 14

If a radius is constant through out a horizontal tube then velocity is constant as well, what does this mean in terms of pressure?

Answer 14

If velocity is constant then acceleration is 0 so the total force must be 0. Making Pressure constant as well (P = F / A)

Question 15

The bernoulli equation is not valid when ____ is present because ______ energy will decrease.

Answer 15

• friction

- mechanical

Question 16

In a blood vessel, erythrocytes closest to the wall are ____ than those in the middle because of ___

Answer 16

slower

friction

Question 17

Friction forces produce a ____ stress

Answer 17

shear

Question 18

Shear stress appears in a blood vessel because

Answer 18

One layer of the fluid moves slower than the other pulling it back.

Question 19

Shear stress in a fluid formula:

Answer 19

F / A = Δ V / Δ y x N

Δy = fluid layer separation
μ = viscosity

Question 20

viscosity ( μ ) units

Answer 20

0.1 Pa x s = 1poise

Question 21

What is the non-stop (no slip) condition ?

Answer 21

The molecules of the wall are so close to the fluid molecules that they assume the v = 0.

Almost as if the molecules closer to the wall are stuck to it

Question 22

Wherever there is a velocity difference there is ____

Answer 22

friction.

Question 23

As mechanical energy decreases what happens to the pressure within one tube with constant radius

Answer 23

Pressure decreases as well

Question 24

What does this mean?

Answer 24

The velocity is greatest at the center and smallest close to the walls

Question 25

Poiseuille’s flow

Answer 25

Δ P = ((8 μ L) / ( π r4 )) Q

Similar to electric V= IR

Question 26

Hydraulic resistance

Answer 26

((8 μ L) / ( π r4 ))

Question 27

If the radius increases what happens to the flow rate?

Answer 27

It increases too

Question 28

If viscosity increases what happens to the flow rate?

Answer 28

It decreases

Question 29

If the length of the pipe increase what happens to the flow rate?

Answer 29

It decreases.

Question 30

Explain the graph

Answer 30

The pressure along the pipe decreases with friction because mechanical energy is lost as heat, and if mechanical energy decreases, so does pressure

Question 31

A decrease in radius (stenosis) does what to the hydraulic resistance?

Answer 31

It increases the hydraulic resistance

Question 32

What happens to the ΔP if hydraulic resistance increase?

Answer 32

It increases too, so does the flow rate

Question 33

Q = (( π r4 ) / (8 μ L) ) represents

Answer 33

conductance (vascular)

Question 34

Effect of more than one vessel in series to the vascular resistance

Answer 34

ΔP T = (r1 x r2 x rn ) Q

Increase of resistance is directly proportional to the number of vessels

Question 35

Effect of more than one vessel in parallel to the vascular resistance

Answer 35

Vascular resistance = resistance of each vessel / number of vessels

Resistance is inversely proportional to the number of vessels.

Question 36

Vascular resistance is _____ proportional to conductance

Answer 36

inversely

Question 37

Friction is more relevant in arterioles than in capillaries because___

Answer 37

There are more capillaries than arterioles.

Analogy to the generation 5-15 in bronchioles

Question 38

Turbulent flow causes

Answer 38

increase in velocity due to decrease area

Question 39

Reynolds number

Answer 39

Re (kinetic energy / friction stress)

Question 40

Low Re numbers =

High Re numbers =

Answer 40

Low = laminar regime (<1000)
High = turbulent regime (> 1500)(jet > 2000)

Question 41

Neutonian fluids have a ____

Answer 41

viscosity