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Systems Phys 2022 > Hemodynamics > Flashcards

Hemodynamics Flashcards

1
Q

What 4 variables influence hemodynamics?

A

pressure

compliance

velocity of blood flow

resistance

Poisuelle’s Law

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2
Q

How does the LV generate pressure?

A

pressure is generated to move blood through tubes through arterial side and back to the RA

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3
Q

How does the RV generate pressure?

A

RV generates pressure that circulates blood through pulmonary circulation through lungs

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4
Q

What happens to transmural pressure (T.P.) when standing?

A

T.P. above the heart is lower

T.P. above the heart is higher

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5
Q

What is an outside influence on B.P.?

A

Gravity

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6
Q

Define: Blood Pressure

A

pressure produced when LV contracts

pressure in vasculature

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7
Q

Define: Transmural Pressure (TP)

A

pressure across the wall

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8
Q

What happens to BP and TP at heart level?

A

they are equal when standing or sitting

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9
Q

What happens to BP and TP while lying down?

A

they are equal

above heart → both 99 mm Hg

at heart → both 100 mmHg

below heart → both 98 mmHg

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10
Q

What happens to BP and TP while standing?

A
  • Above Heart
    • BP → 99 mmHg
    • TP → 69 mmHg
  • At Heart
    • BP → 100 mmHg
    • TP → 100 mmHg
  • Below Heart
    • BP → 98 mmHg
    • TP → 198 mmHg
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11
Q

Is compliance higher in veins or arterial system?

A

veins

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12
Q

Equation: Compliance

A

Compliance = ΔV/ΔP

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13
Q

Define: Compliance

A

characteristic of any hollow organ or vessel

lowest when volume in chamber is smallest

as you fill a chamber closer to its max volume, compliance will be reduced

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14
Q

What is the most compliant part of the arterial system?

A

Thoracic aorta

70/40 = 1.75

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15
Q

What happens when you increase you increase sympathetic stimulation to the veins?

A

NE is released → NE binds α1 receptor → cause contraction of smooth muscle → decrease in vein compliance

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16
Q

Why is compliance less important to arteries?

A

B/c they have less blood

it primarily effects shape of aortic pressure pulse

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17
Q

What happens if you increase sympathetic tone to arterial side?

A

increases resistance

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18
Q

Why is compliance important to veins?

A

if you decreases compliance of the veins → walls become more rigid → pressure increases → increases venous return to heart → preload increases → SV increases → CO increases

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19
Q

What is the relationship between a cross sectional area and velocity flow?

A

inverse

area increases → velocity of flow decreases

area decreases → velocity of flow increases

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20
Q

What system has the largest cross sectional area?

A

capillaries → slowest velocity → helps drive diffusion

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21
Q

What are the 2 components to pressure of flowing blood?

A

lateral or static

kinetic

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22
Q

what happens to kinetic component at a higher flow velocity?

A

it is greater

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23
Q

What happens when a patient has atherosclerotic plaque?

A

Increased velocity flow → lateral pressure (to kidneys) drops → kidneys get less blood flow → can cause HTN

24
Q

What occurs during narrowing of aortic valve?

A

contraction is restricted → increased velocity blood flow → reduce lateral blood flow

25
Q

Equation: Resistance

A

resistance = ΔP(pressure)/Q(volume flow)

26
Q

To get resistance in whole circulatory system (systemic circulation), where would you need to measure pressures in order to know ΔP?

Assume pressure in aorta is 120/80 and RA pressure is ~ 2mmHg

A

System starts in the aorta → need to know mean/avg pressure in aorta (maBP= diastolic + ⅓ PP)

maBP = 80 + ⅓(40) = 93 mmHg

system ends where vena cava enters RA

TPR = ΔP/Q= (93-2)/5 = 91/5

27
Q

Equation: maBP

A

maBP = diastolic + ⅓ PP

28
Q

Equation: Pulse Pressure

A

Systolic - Diastolic

29
Q

Equation: TPR

A

TPR Δ in pressure across the system

TPR = ΔP/Q

30
Q

What does resistance depend on in the circulatory system?

A

arterioles (are they constricted or relaxed)

31
Q

What do you regulate by changing resistance?

A

pressure and volume flow

32
Q

What happens if you constrict arterioles?

A

Pressure in aorta increases

pressure in capillaries decreases

volume flow through arterioles drops

33
Q

What are the special conditions required for Poiseuille’s Law to apple?

A
  • Flow is non-pulsatile (no flow variations with time)
  • Flow is laminar
  • The fluid is a newtonian fluid (homogeneous fluid such as water; no a suspension like blood)
34
Q

What variables does Poiseuille’s Law relate?

A

pressure

length of tube

radius of tube

viscosity of the liquid

35
Q

Does the circulatory system meet the criteria for Poiseuille’s Law?

A

No, but the relationships still influence blood flow

36
Q

What does flow through a tube depend on?

A

inflow and outflow pressures

37
Q

What happens to volume flow if you double the pressure and increase the height of a system?

A

double the flow

38
Q

What happens to volume flow if you reduce the difference of a system?

A

pressure of flow decreases

39
Q

What happens to volume flow if there is no difference in pressure and hieght of a system?

A

there is no flow

40
Q

What is the relationship between flow and ΔP?

A

they are directly proportional

they greater the ΔP, the greater the flow

41
Q

What is the relationship between length of the tube and volume flow?

A

inverse relationship

Increase tube length, decrease flow

42
Q

What is the relationship between radius of the tube and volume flow?

A

directly proportional

increase radius, increase flow

43
Q

What is the relationship between viscosity of the liquid and volume flow?

A

inversely proportional

increase viscosity, decrease flow

44
Q

Define: Viscosity

A

a measure of how difficult it is to separate lamina (relatively constant in circulatory system)

45
Q

How does liquid flow in a tube?

A

faster in the center

slower on the periphery

46
Q

What effect does hematocrit have on viscosity?

A

Increase hematocrit, increase viscosity

can change viscosity by changing hematocrit

47
Q

Define: Hematocrit

A

percent of RBCs present in blood

48
Q

Equation: Velocity flow

A

Q = π(Pi-Po)r4/8nl

r = radius

l = length

n = viscosity

49
Q

Which variable from the volume flow equation varies the most in the circulatory system?

A

r4

50
Q

Where does the greatest change in pressure occur?

A

Arterioles

51
Q

How are resistors organized in a circulatory system?

A

in parallel

52
Q

What would happen if the resistors were organized in series?

A

total resistance of a series = sum of all resistors

more organs in series → greater resistance → increase work for heart → increase metabolic demands → less efficient

53
Q

What does the resistors being in parallel allow the circulatory system to do?

A

It allows varying flow to different organs

adding another resistor reduces heart work

54
Q

What are the parts of the arterial pulse wave?

A

Incisura or Dicrotic notch → aortic valve closes, ejection phase ends

Dicrotic wave → Dicrotic notch to diastole

Systolic pressure → highest pressure during 1 cardiac cycle ,increases as you move away from heart

mean pressure → diastolic + ⅓PP

diastolic pressure → lowest pressure

55
Q

What happens to compliance of the aorta as you move away from the heart?

A

it decreases

56
Q

What are peripheral arterial blood pressure and volume flow affected by?

A

Changes in vascular compliance, total peripheral resistance, and stroke volume

Systems Phys 2022 (25 decks)

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