Systemic Circulation

Question 1

What is the formula for La Place’s Law?

Answer 1

T = P x r (for a cylinder) and T = (P x r)/2 for a sphere

Question 2

What is the formula for La Place’s Law?

Answer 2

T = P x r (for a cylinder) and T = (P x r)/2 for a sphere

Question 3

For a graph of pressure vs. volume (pressure on the X and volume on the Y) what does the slope equal?

Answer 3

Compliance.

Question 4

Which are more compliant, veins or arteries?

Answer 4

Veins (at low pressure, eventually their compliance will increase)

Question 5

For a graph of volume (X) vs. pressure (Y) what does the slope equal?

Answer 5

1/compliance. It is the elasticity.

Question 6

What happens to vascular compliance with age?

Answer 6

It decreases.

Question 7

What is the formula for MAP?

Answer 7

MAP = P_D + 1/3 PP

Question 8

Can vascular compliance be regulated?

Answer 8

Vascular compliance is determined by arrangement of elastic fibers and smooth muscle and is not homeostatic ally regulated parameter like pressure.

Question 9

Low volume capacity, modest expansion and maintained resistance over wide pressure levels describes what vessel type?

Answer 9

Arteries. Thus arteries function as resistance vessels.

Question 10

What vessels have the ability to expand greatly with small pressure changes (due to the high compliance) and have large volume changes?

Answer 10

Veins. They act as volume reservoirs or capacitance vessels.

Question 11

What is the Windkessel effect? Why does it dampen the flow changes seen for a non-distensible vessel?

Answer 11

It is the storage of blood during systole and the consequence is the maintenance of blood flow during diastole. The Aorta, pulmonary artery and their major branches store a volume of blood and elastic energy that during systole and then deliver this blood into the peripheral vessels during diastole. The low resistance to blood flow and distensibility allow this to occur.

Question 12

What is the Windkessel effect?

Answer 12

It is the storage of blood during systole and the consequence is the maintenance of blood flow during diastole. The Aorta, pulmonary artery and their major branches store a volume of blood and elastic energy that during systole and then deliver this blood into the peripheral vessels during diastole. The low resistance to blood flow and distensibility allow this to occur.

Question 13

For a graph of pressure vs. volume (pressure on the X and volume on the Y) what does the slope equal?

Answer 13

Compliance.

Question 14

Which are more compliant, veins or arteries?

Answer 14

Veins (at low pressure, eventually their compliance will increase)

Question 15

For a graph of volume (X) vs. pressure (Y) what does the slope equal?

Answer 15

1/compliance. It is the elasticity.

Question 16

What happens to vascular compliance with age?

Answer 16

It decreases.

Question 17

What is the formula for MAP?

Answer 17

MAP = P_D + 1/3 PP

Question 18

Can vascular compliance be regulated?

Answer 18

Vascular compliance is determined by arrangement of elastic fibers and smooth muscle and is not homeostatic ally regulated parameter like pressure.

Question 19

Low volume capacity, modest expansion and maintained resistance over wide pressure levels describes what vessel type?

Answer 19

Arteries. Thus arteries function as resistance vessels.

Question 20

What vessels have the ability to expand greatly with small pressure changes (due to the high compliance) and have large volume changes?

Answer 20

Veins. They act as volume reservoirs or capacitance vessels.

Question 21

What is Raynaud’s syndrome?

Answer 21

It is a disorder marked by brief episodes of vasospasm, which is a narrowing of the blood vessel diameter. The digits turn white, then blue, then back to red as they are reperfused.

Question 22

What is the Windkessel effect?

Answer 22

It is the storage of blood during systole and the consequence is the maintenance of blood flow during diastole. The Aorta, pulmonary artery and their major branches store a volume of blood and elastic energy that during systole and then deliver this blood into the peripheral vessels during diastole. The low resistance to blood flow and distensibility allow this to occur.

Question 23

What is Pulse Pressure? What is it proportional to?

Answer 23

It is the difference between systolic and diastolic pressure. It is proportional to SV and 1/C. So with age as compliance goes down PP can go up.

Question 24

In the case of hypotensive shock or hemorrhagic shock what does the body do to compensate?

Answer 24

A sympathetic response, i.e. contraction of smooth muscle, would lower the void volume, shifting the compliance curves to the left (Volume vs. Pressure graph). Blood pressure will be maintained at lower volume by this adjustment mechanism.

Question 25

What effect does sympathetic stimulation have on critical closing pressure?

Answer 25

Without sympathetic stimulation the closing pressure is around ~6mmHg, with sympathetic stimulation it increases to ~40mmHg. Blood flow can completely stop in the limbs despite the persistence of even small pressure differences between the main artery and vein.