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Physiology Cardio > Hemodynamics > Flashcards

Hemodynamics Flashcards

1
Q

Relationship between velocity and flow

A

V=Q/A

Q = flow (cm^2/s)

A = cross-sectional area

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2
Q

If no branching…

And the cross sectional area increases…

The flow will

A

Stay the same

(Velocity decreases)

**if branching…flow can change

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3
Q

Cross-sectional area is largest in the ?

A

Capillaries…

So velocity is much lower in capillaries compared to the aorta and bigger arteries

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4
Q

Turbulent flow

A

Disordered, inefficient flow

Not ideal

Can do damage to the endothelium

Occurs at branch points and points with vessel narrowing

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5
Q

Laminar flow

A

Most efficient type of flow

Concentric layers of flow

Layers closer to the walls = slower due to friction

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6
Q

Reynolds number

A

Re = pDv/n

P = density
D = diameter
V = velocity
N = viscosity

Greater than 200 = turbulent

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7
Q

Factors that would increase reynolds number and turbulency

A

Increased blood density, velocity, and vessel diameter

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8
Q

Factors that decrease reynolds number and turbulency

A

Increased blood viscosity

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9
Q

Anemia effecy on Re

A

Decreases viscosity —> increases Re

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10
Q

Increased CO —> Re?

A

Increases velocity —> increases Re

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11
Q

Decreased vessel diamter —> Re?

A

Increases velocity —> increases Re

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12
Q

Dramatic increase in systolic pressure in the external or internal carotid in comparison to the common and other carotid = sign of what

A

Stenosis of one of the carotid branches…thus directing much of the blood flow to the other…instead of splitting the flow between the two after bifurcation

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13
Q

Pulse pressure =

A

Difference between systolic and diastolic pressures

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14
Q

Mean arterial pressure

A

Diastolic pressure + 1/3*pulse pressure

Is the area under the graph of arterial pressure over the period of one cardiac cycle

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15
Q

Distensibility

A

Ability to change dimension in response to force

Ensure steady flow

Reduces the amount of work the heart has to do

Rigid vessels over time can lead to heart failure

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16
Q

Compliance

A

Change in volume for a given change in pressure (deltaV/deltaP)

Measure of how distensible vessels are

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17
Q

Elasticity

A

Ability to return to normal size after being distended

Lost over time/age

Which causes an increase in systolic pressure, and since diastolic pressure remains the same…pulse pressure increases with age

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18
Q

Ohm’s law for blood flow

A

Q = delta P/R

Q = flow. (Was current)

P = pressure (was voltage)

19
Q

Poiseuille’s law

A

Replaces R with an equation in Ohm’s

R = 8(viscosity)(length)/pi*radius^4

Sub into Ohm’s law

20
Q

Effect of the following on flow

  1. Decrease viscosity
  2. Increase viscosity
  3. Decreased radius
  4. Increased radius
  5. Decreased length
  6. Increased length
A
  1. Up (anemia)
  2. Down (polycythemia)
  3. Down (vasoconstriction)
  4. Up (vasodilation)
  5. Up (rare)
  6. Down (rare)
21
Q

Total resistance for vessels in a series =

A

Resistances added up

Benefit = allows laminar flow

But otherwise cannot just have series because of increasing resistance…blood wouldn’t get back to the heart

22
Q

Total resistance with vessels in parallel

A

Inverse of total = inverse of each individual

Overall resistance is lowered

Benefit = can shunt blood from one vessel to another depending on the resistance

23
Q

Does viscosity of blood constant?

A

No

Not a Newtonian fluid…

Why?

  1. Blood viscosity increases with increasing hemacrit
  2. Fahraeus-Lingqvist effect = small diameter vessels, red blood cells move toward the center of … so outer part being more fluid…becomes less viscous and less friction
  3. Blood viscosity decreases with increased flow
24
Q

Compare primary functions of arteries, veins, and capillaries

Relate those differences in structure

A
  1. Arteries:
    - lots of smooth muscle to handle force of blood pumping through it
    -adventitia secures arteries in place
    -ENDOTHELIAL LAYER
    —> separates blood from smooth muscle…receives signals and sends messenges that cause smooth to constrict or dilate

1A. Arterioles

  • responsible for regulating total peripheral resistance
  • vasoconstriction = increased pressure upstream and decreased downstream…

1B. Metaarterioles

  • connects arterioles to venules
  • bypasses flow directly from arteriole to venule
  • allows completely shunt blood away from capillaries or just some
  1. Veins
    - just enough of SmM for constriction and dilation
    Valves allow for unidirectional flow and compartmentalization
    - highly distensible - allows them to hold high volume for reservoir purposes
  2. Capillaries
    - single layer of endothelial cells
    - sites for exchange with surrounding tissue
25
Q

Why the drastic drop in pressure moving from muscular arteries to capillaries

A

Compensates for the increase in resistance in the capillaries

26
Q

Law of LaPlace

A

T = P * r

T = wall tension
P = transmural pressure 
R = radius

**capillaries can withstand a elevated “P” due to a small radius

Aneurysms

—> arteries remodel themselves to cope with an increasing wall tension - bulging to make a sphere shape

27
Q

In order for diffusion to happen…the substance must be what is nature?

A

Hydrophobic

28
Q

Fick’s Law

A

Diffusion in the capillary follows this law

J = -PS (Co - Ci)

J = movement of solute over time
P = each substance diffusing across has a different eas of diffusion
S = surface area, as you increase S...easier to get inside 
C = concentrations inside/out (gradient...most important factor)
29
Q

Edema affect on diffusion across capillary

A

You have liquid that is pushing on the tissue …adding distance between the capillary and tissue

Once this happens…diffusion becomes diffusion limited…you have to wait for material to make its way to the tissue

30
Q

Filtration

A

Capillary —> interstitial fluid

Capillaries have a higher pressure, fluids push into fluid

Driven by hydrostatic pressure…but it decreases as you approach the venule

31
Q

Absorption

A

As you get to the venules…hydrostatic pressure diminishes and now the dominant pressure is oncotic pressure

Which is formed by plasma proteins in the plasma (mostly albumin) in the capillary…these proteins will start to pull water into capillary

32
Q

Sterling equation

A

Summarizes the flow of fluid is equal to the difference in hydrostatic pressure minus the difference in oncotic pressure

The drop is pressure from arteriole to venule serves as a change from filtration —> absorption

If difference in HSP > difference OP = filtration (positive #)

33
Q

Goal of vasodilation?

Vasoconstriction?

A

Vasoconstriction:

Causes pressure to decrease DOWNSTREAM in the capillaries

Leads to a DECREASE in filtration and INCREASE in absorption —> leads to restoration of blood volume

Vasodilation:

Causes pressure to increase DOWNSTREAM in the capillaries

Leads to INCREASE filtration and DECREASE absorption —> leads to edema

34
Q

Pinocytosis

A

Method by which you get large lipid insoluble molecules into the cell

35
Q

Effects of vasodilation of arterioles on filtration and absorption

Vasoconstriction of arterioles

A

Increased pressure on arterilar side…

Increased filtration and decreased absorption

—> more fluid entering into the interstitial space.

Constriction = opposite

36
Q

Function of lymphatic system…

A

Vessels intercalated by capillary bed

Pressure within bed is lower than pressure within the capillaries…so fluid can flow into them

Main importance = helps resotre blood to its normal volume

Prevents edema

37
Q

Deep vein thrombosis (DVT)

A

Caused by clot forming in the venous side…restricting blood flow

Messing up the flow —> increase in venous pressure —> similar effect as if you vasodilated the arterioles

Increase filtration and decrease absorption

38
Q

Decrease pressure on arteriolar side

Effect?

A

Enhanced reabsorption

Cause = vasoconstriction

39
Q

Increased pressure on the arteriolar side

Effect?

A

Enhanced filtration/edema

Cause = vasodilation

40
Q

Increased pressure on venous side

A

Effect = enhanced filtration/edema (same as increasing arteriolar pressure)

Cause = heart failure, venous clots

41
Q

Decreased pressure on venous side

Effect =?

A

Effect = enhanced reabsorption (same as decreased pressure on arteriolar side)

Cause = hemorrhage

Need to restore blood volume

42
Q

Why does tension remain low in capillaries? Veins?

A

Capillaries have a small radius

Veins have little pressure

Refer to Law of LaPlace: T = P x R

43
Q

What characteristic of veins allow them to make good ‘reservoirs’ of blood?

A

They have high compliance

Takes a small change in pressure to instill a large change in volume

Physiology Cardio (11 decks)

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