Systemic Circulation

Question 1

what are the three axes of pressure?

Answer 1

radial axis, axis of vessel and axis of transmral pressure

Question 2

what is the slope of the relative volume vs transmural pressure graph?

Answer 2

compliance

Question 3

what is the pressure range of the aorta?

Answer 3

0-250 mmHg

Question 4

how does the compliance of veins compare to that of the aorta? what is a physiologic implication of this?

Answer 4

much greater

should be a consideration when transplanting a vein to bypass an artery

Question 5

what is the physiologic range of venous pressure?

Answer 5

15 mmHg or less

Question 6

what is an implication of the high compliance of veins?

Answer 6

they hold much more blood than arteries

Question 7

what are the axes of a graph with a slope of elastance?

Answer 7

volume is the x axis and pressure in the y axis

Question 8

what is the implication of the low compliance of arteries when considering blood loss?

Answer 8

pressure drops quickly in response to change in volume

Question 9

what can cause a change in the compliance curve of a blood vessel?

Answer 9

vasomotor tone

Question 10

how does the compliance of vessels change with age?

Answer 10

younger people have more compliant vessels than older people because of remodeling of connective tissue throughout life

Question 11

how does a high compliance vessel respond to pulsatile flow?

Answer 11

there is less response to flow with the changing of pressure. in high pressure the vessel holds more volume to prevent a large increase in flow. during low pressure, this excess volume flows out of the vessel

Question 12

why is diastolic pressure not zero?

Answer 12

because of the compliance of blood vessels

Question 13

when does the pressure in the left ventrical coordinate with the pressure in the aorta?

Answer 13

when the aortic valve is open

Question 14

what is an equation for partial pressure?

Answer 14

stroke volume/compliance

Question 15

what is transmural pressure and what is it equal to?

Answer 15

it is the pressure across the vessel wall and it is equal to the blood pressure

Question 16

what is the equation for tension in a blood vessel?

Answer 16

T=P x r (transmural pressure x radius)

Question 17

how does the tension in a large vessel compare to that of a small vessel at the same pressure? what pathophysiological conditions involve this mechanism?

Answer 17

it is greater

implicated in aneurisms (increase in tension) and stenosis (decrease in tension)

Question 18

what is the critical closing pressure?

Answer 18

the pressure below which the vessel will be closed due to the “floppiness” of the vessel

Question 19

during blood loss, what does the high compliance of the venous system cause?

Answer 19

a small displacement in blood pressure will mobilize a large volume from the venous blood (increasing venous return)

Question 20

how does sympathetic stimulation affect the compliance of blood vessels during blood loss?

Answer 20

all vessels are constricted moving their compliance curves to operate at lower volumes to prevent a drop in arterial blood pressure and mobilizing venous reserves

Question 21

what is the pathological mechanism of Raynaud’s syndrome?

Answer 21

brief episodes of vasospasm narrow the blood vessels (mostly in hands) and increases the critical closing pressure causing the vessels to collapse