Hemodynamics

Question 1

What 4 variables influence hemodynamics?

Answer 1

pressure

compliance

velocity of blood flow

resistance

Poisuelle’s Law

Question 2

How does the LV generate pressure?

Answer 2

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

Question 3

How does the RV generate pressure?

Answer 3

RV generates pressure that circulates blood through pulmonary circulation through lungs

Question 4

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

Answer 4

T.P. above the heart is lower

T.P. above the heart is higher

Question 5

What is an outside influence on B.P.?

Answer 5

Gravity

Question 6

Define: Blood Pressure

Answer 6

pressure produced when LV contracts

pressure in vasculature

Question 7

Define: Transmural Pressure (TP)

Answer 7

pressure across the wall

Question 8

What happens to BP and TP at heart level?

Answer 8

they are equal when standing or sitting

Question 9

What happens to BP and TP while lying down?

Answer 9

they are equal

above heart → both 99 mm Hg

at heart → both 100 mmHg

below heart → both 98 mmHg

Question 10

What happens to BP and TP while standing?

Answer 10

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

Question 11

Is compliance higher in veins or arterial system?

Answer 11

veins

Question 12

Equation: Compliance

Answer 12

Compliance = ΔV/ΔP

Question 13

Define: Compliance

Answer 13

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

Question 14

What is the most compliant part of the arterial system?

Answer 14

Thoracic aorta

70/40 = 1.75

Question 15

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

Answer 15

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

Question 16

Why is compliance less important to arteries?

Answer 16

B/c they have less blood

it primarily effects shape of aortic pressure pulse

Question 17

What happens if you increase sympathetic tone to arterial side?

Answer 17

increases resistance

Question 18

Why is compliance important to veins?

Answer 18

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

Question 19

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

Answer 19

inverse

area increases → velocity of flow decreases

area decreases → velocity of flow increases

Question 20

What system has the largest cross sectional area?

Answer 20

capillaries → slowest velocity → helps drive diffusion

Question 21

What are the 2 components to pressure of flowing blood?

Answer 21

lateral or static

kinetic

Question 22

what happens to kinetic component at a higher flow velocity?

Answer 22

it is greater

Question 23

What happens when a patient has atherosclerotic plaque?

Answer 23

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

Question 24

What occurs during narrowing of aortic valve?

Answer 24

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

Question 25

Equation: Resistance

Answer 25

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

Question 26

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

Answer 26

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

Question 27

Equation: maBP

Answer 27

maBP = diastolic + ⅓ PP

Question 28

Equation: Pulse Pressure

Answer 28

Systolic - Diastolic

Question 29

Equation: TPR

Answer 29

TPR Δ in pressure across the system TPR = ΔP/Q

Question 30

What does resistance depend on in the circulatory system?

Answer 30

arterioles (are they constricted or relaxed)

Question 31

What do you regulate by changing resistance?

Answer 31

pressure and volume flow

Question 32

What happens if you constrict arterioles?

Answer 32

Pressure in aorta increases pressure in capillaries decreases volume flow through arterioles drops

Question 33

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

Answer 33

* 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)

Question 34

What variables does Poiseuille's Law relate?

Answer 34

pressure length of tube radius of tube viscosity of the liquid

Question 35

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

Answer 35

No, but the relationships still influence blood flow

Question 36

What does flow through a tube depend on?

Answer 36

inflow and outflow pressures

Question 37

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

Answer 37

double the flow

Question 38

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

Answer 38

pressure of flow decreases

Question 39

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

Answer 39

there is no flow

Question 40

What is the relationship between flow and ΔP?

Answer 40

they are directly proportional they greater the ΔP, the greater the flow

Question 41

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

Answer 41

inverse relationship Increase tube length, decrease flow

Question 42

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

Answer 42

directly proportional increase radius, increase flow

Question 43

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

Answer 43

inversely proportional increase viscosity, decrease flow

Question 44

Define: Viscosity

Answer 44

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

Question 45

How does liquid flow in a tube?

Answer 45

faster in the center slower on the periphery

Question 46

What effect does hematocrit have on viscosity?

Answer 46

Increase hematocrit, increase viscosity can change viscosity by changing hematocrit

Question 47

Define: Hematocrit

Answer 47

percent of RBCs present in blood

Question 48

Equation: Velocity flow

Answer 48

Q = π(Pi-Po)r⁴/8nl r = radius l = length n = viscosity

Question 49

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

Answer 49

r⁴

Question 50

Where does the greatest change in pressure occur?

Answer 50

Arterioles

Question 51

How are resistors organized in a circulatory system?

Answer 51

in parallel

Question 52

What would happen if the resistors were organized in series?

Answer 52

total resistance of a series = sum of all resistors more organs in series → greater resistance → increase work for heart → increase metabolic demands → less efficient

Question 53

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

Answer 53

It allows varying flow to different organs adding another resistor reduces heart work

Question 54

What are the parts of the arterial pulse wave?

Answer 54

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

Question 55

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

Answer 55

it decreases

Question 56

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

Answer 56

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