Lecture 15: Hemodynamics and Systemic Circulation Part I

Question 1

Which vasculature has the highest and lowest pressure?

Answer 1

Highest pressure: arteries

Lowest pressure: veins

Question 2

Which vasculature has the highest amount of volume for blood?

Answer 2

Veins (65% total blood volume)

Question 3

When veins constrict, what happens to the blood?

Answer 3

Can move blood to arterial side to increase blood pressure

*change in volume but not much with resistance

Question 4

When arteries constrict, what happens to the blood?

Answer 4

There is a change in resistance but not much with volume

Question 5

How do you calculate the velocity of blood flow?

Answer 5

Velocity = Flow/Area

Question 6

How do you calculate blood flow?

Answer 6

Flow = Pressure Gradient/Resistance

Question 7

How do you calculate cardiac output?

Answer 7

Cardiac Output = (Arterial - Venous Pressure)/Total Peripheral Resistance

Question 8

What factors can affect resistance?

Answer 8

Viscosity
Length of Vessel
Radius of Vessel (biggest factor)

Question 9

Adding resistance beds in series _____ resistance

Answer 9

Adding resistance beds in series INCREASES resistance (the longer the tube the higher the resistance)

Question 10

Adding resistance beds in parallel _____ resistance

Answer 10

Adding resistance beds in parallel DECREASES resistance (the more divisions the blood goes through, the less resistance)

Question 11

What is laminar flow?

Answer 11

Smooth blood flow with little turbulence (high velocity in center and lower velocity in the sides)
<2000

Question 12

What is the Reynolds number equation?

Answer 12

Reynolds Number = (density x diameter x velocity)/Viscosity

*Becomes more turbulent is there is an increase in density, diameter, velocity or decrease in viscosity

Question 13

What is compliance?

Answer 13

How easy for vessel to expand

Question 14

What is the formulate to calculate compliance?

Answer 14

Compliance = (Δvolume)/(Δ pressure)

Question 15

Which type of blood vessel has the greatest compliance?

What vessel has the lowest compliance?

Answer 15

Veins

Arteries, even lower when arteries are aged (as in atherosclerosis)

Question 16

When veins constrict, what happens to its compliance?

Answer 16

Volume is reduced so compliance decreases

• blood shifts to arterial side, increasing arterial blood pressure
• can change diameter and compliance stays the same

Question 17

Why is there a pulsatile nature in the blood pressure from aorta to small arteries? How does this relate to systolic and diastolic pressures?

Answer 17

Due to compliance and distension during ejection and recoil during diastole
Systolic is highest pulsatile point and diastolic is lowest pulsatile point

Question 18

How do you calculate pulse pressure?

Answer 18

Pulse Pressure = Systolic - Diastolic

Question 19

How do you calculate mean pressure?

Answer 19

Mean Pressure = Diastolic + ⅓ Pulse Pressure

Question 20

How does blood volume in lungs compare to aorta?

How does resistance and pressure in lungs compare to aorta?

Answer 20

• same

- both lower in lungs than aorta

Question 21

If there is a decrease in compliance, what would happen to pulse pressure?

Answer 21

It will increase (mostly the systolic pressure, diastolic will stay the same or decrease)
*think about compliance formula

Question 22

If there is a increase in resistance, what would happen to pulse pressure?

Answer 22

Stays the same

-if cardiac output and stroke volume stays the same

Question 23

How is left atrial pressure measured?

Why?

Answer 23

Use a catheter through jugular vein –> RA –> RV –> pulmonary vein and blow up a balloon

• pressure measured here is related to Left Atrium pressure
• good sign of cardiac failure

Question 24

What is cardiac failure?

Answer 24

Left ventricle cannot properly pump blood efficiently