Cardiac biophysics Flashcards

1
Q

Blood is a _____ and ____ fluid

A

complex and incompressible

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2
Q

Pressure is a ____ force always present

A

compressive

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3
Q

Velocity is high in ____ vessels

A

large

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4
Q

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

A

pressure.

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5
Q

Arterial pressure is _____ over the atmospheric pressure

A

120 mmHg

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6
Q

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

A

equal

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7
Q

Flow rate (Q) formula

A

Q = Δ V / Δ t

Q = V x A

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8
Q

How would we find the Q?

A

V1 x A1 = V3 [A3 x n3]

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9
Q

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

A

Velocity decreases

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10
Q

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

A

Q = V x A

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

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11
Q

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

A

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

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12
Q

What does the Bernoulli equation represent ?

A

The mechanical energy in a fluid

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13
Q

Bernoulli equation:

A

P + 1/2 ρ v2 + ρgh = cte in a fluid

1/2 ρ v2 = kinetic energy

ρgh = potential energy

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14
Q

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

A

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

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15
Q

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

A
  • friction

- mechanical

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16
Q

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

A

slower

friction

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17
Q

Friction forces produce a ____ stress

18
Q

Shear stress appears in a blood vessel because

A

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

19
Q

Shear stress in a fluid formula:

A

F / A = Δ V / Δ y x N

Δy = fluid layer separation
μ = viscosity

20
Q

viscosity ( μ ) units

A

0.1 Pa x s = 1poise

21
Q

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

A

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

22
Q

Wherever there is a velocity difference there is ____

23
Q

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

A

Pressure decreases as well

24
Q

What does this mean?

A

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

25
Poiseuille’s flow
Δ P = ((8 μ L) / ( π r4 )) Q Similar to electric V= IR
26
Hydraulic resistance
((8 μ L) / ( π r4 ))
27
If the radius increases what happens to the flow rate?
It increases too
28
If viscosity increases what happens to the flow rate?
It decreases
29
If the length of the pipe increase what happens to the flow rate?
It decreases.
30
Explain the graph
The pressure along the pipe decreases with friction because mechanical energy is lost as heat, and if mechanical energy decreases, so does pressure
31
A decrease in radius (stenosis) does what to the hydraulic resistance?
It increases the hydraulic resistance
32
What happens to the ΔP if hydraulic resistance increase?
It increases too, so does the flow rate
33
Q = (( π r4 ) / (8 μ L) ) represents
conductance (vascular)
34
Effect of more than one vessel in series to the vascular resistance
ΔP T = (r1 x r2 x rn ) Q Increase of resistance is directly proportional to the number of vessels
35
Effect of more than one vessel in parallel to the vascular resistance
Vascular resistance = resistance of each vessel / number of vessels Resistance is inversely proportional to the number of vessels.
36
Vascular resistance is _____ proportional to conductance
inversely
37
Friction is more relevant in arterioles than in capillaries because___
There are more capillaries than arterioles. | Analogy to the generation 5-15 in bronchioles
38
Turbulent flow causes
increase in velocity due to decrease area
39
Reynolds number
Re (kinetic energy / friction stress)
40
Low Re numbers = | High Re numbers =
``` Low = laminar regime (<1000) High = turbulent regime (> 1500)(jet > 2000) ```
41
Neutonian fluids have a ____
viscosity