11/18/2014 Medical Physiology Principles of Blood Flow Barry Knox

Question 1

Describe the graph of blood pressure.

Answer 1

Coordinates are Pressure vs. Time. 1. Height of graph - systolic pressure 2. Nadir of graph - diastolic pressure 3. Dichrotic notch - found in time, just after the height of systolic pressure

Question 2

What is pulse pressure?

Answer 2

SP - DP

Question 3

What is mean arterial pressure?

Answer 3

DP + 1/3PP The average pressure over the entire cardiac cycle

Question 4

What causes the dicrotic notch?

Answer 4

The dicrotic notch is a dip right after the height of the systolic pressure, caused by the backfilling of the aortic valve as it closes.

Question 5

What is the normal PP?

Answer 5

About 40 mmHg (120-80)

Question 6

T/F: Blood is a Newtonian fluid.

Answer 6

False. Blood is a non-Newtonian fluid.

Question 7

Flow in a series tube is:

Answer 7

constant, no matter the size of the vessel, Q1=Q2=Q3

Question 8

Flow in a parallel circuit is:

Answer 8

Additive Q = Q1 + Q2 + Q3

Question 9

T/F: In order to avoid hypoxia, the flow of oxygen in the arteries to the tissues must be equal to or greater than the rate of oxygen consumption by the tissues.

Answer 9

True

Question 10

In the parallel architecture of the cardiovascular system, the flow of oxygen is distributed to each tissue at rest in accordance with what?

Answer 10

The metabolic needs of the tissue

Question 11

Dramatic increases in blood flow to the skin, muscles, and heart during exercise as the venous reserve is mobilized, blood flow to what organ is maintained?

Answer 11

The brain

Question 12

What is the equation for flow (mL O2/min)?

Answer 12

Flow = CO x Arterial O2 content mL O2/min = (L blood/min)x(mL O2/L blood)

Question 13

During exercise, what organ sees the most increased blood flow?

Answer 13

Skin

Question 14

Q=

Answer 14

Av A1v1 = A2v2

Question 15

A man has a CO of 5 L/min. The diameter of his aorta is 25 mm and the total SA of the systemic capillaries is estimated to be 2500cm². What is the relative velocity of his blood in capillaries vs. aorta?

Answer 15

Q = Av A = πr² 1 L = 1000cm²

d/2 = r = 12.5mm = 1.25 cm²

Aorta and capillaries are in series, therefore volume flow is the same.

Aaorta = π(1.25)² = 4.9cm² 5 L/min = 5000 cm²/min

v aorta = Q/A = 5000/4.9 = 1020 cm/min = 17 cm/s

v capillaries = Q/A = 5000/2500 = 2 cm/min = 0.033 cm/s

v aorta/v capillaries = 2500/4.9 = 510

Question 16

Give the two equations for transit time required for a blood cell to travel between two points in the system.

Answer 16

t = V/Q (volume/flow)

t = I/v (length/velocity)

Question 17

If capillary blood velocity is 500 microns/s, and capillary length is 0.5 mm, then the capillary transit time is?

Answer 17

t = l/v 1 mm = 1000 microns

0.5 mm –> 500 microns

500 micons/500 microns/s

t = 1 s

Question 18

The total circulation time for one pass through thr entire systemic and pulmonary circulation is about how long?

Answer 18

1 min

Question 19

What is the relationship between blood flow and pressure?

Answer 19

Q = P/R

Question 20

What are the frictional forces in blood flow?

Answer 20

Viscosity of flow

Resistance (walls of vessel)

Question 21

When shoveling snow, the cold temperature increases blood viscosity, contributing to what kind of flow change of blood in the fingers? Is there heat loss or gain?

Answer 21

Decreased blood flow (sludging)

Decreased heat loss

Question 22

The more branches in a parallel network, the ___ the total resistance.

Answer 22

Lower

Question 23

Why do individual capillaries have high resistance?

Answer 23

Radius of the vessels are small