Systemic Circulation Flashcards
what are the three axes of pressure?
radial axis, axis of vessel and axis of transmral pressure
what is the slope of the relative volume vs transmural pressure graph?
compliance
what is the pressure range of the aorta?
0-250 mmHg
how does the compliance of veins compare to that of the aorta? what is a physiologic implication of this?
much greater
should be a consideration when transplanting a vein to bypass an artery
what is the physiologic range of venous pressure?
15 mmHg or less
what is an implication of the high compliance of veins?
they hold much more blood than arteries
what are the axes of a graph with a slope of elastance?
volume is the x axis and pressure in the y axis
what is the implication of the low compliance of arteries when considering blood loss?
pressure drops quickly in response to change in volume
what can cause a change in the compliance curve of a blood vessel?
vasomotor tone
how does the compliance of vessels change with age?
younger people have more compliant vessels than older people because of remodeling of connective tissue throughout life
how does a high compliance vessel respond to pulsatile flow?
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
why is diastolic pressure not zero?
because of the compliance of blood vessels
when does the pressure in the left ventrical coordinate with the pressure in the aorta?
when the aortic valve is open
what is an equation for partial pressure?
stroke volume/compliance
what is transmural pressure and what is it equal to?
it is the pressure across the vessel wall and it is equal to the blood pressure
what is the equation for tension in a blood vessel?
T=P x r (transmural pressure x radius)
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?
it is greater
implicated in aneurisms (increase in tension) and stenosis (decrease in tension)
what is the critical closing pressure?
the pressure below which the vessel will be closed due to the “floppiness” of the vessel
during blood loss, what does the high compliance of the venous system cause?
a small displacement in blood pressure will mobilize a large volume from the venous blood (increasing venous return)
how does sympathetic stimulation affect the compliance of blood vessels during blood loss?
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
what is the pathological mechanism of Raynaud’s syndrome?
brief episodes of vasospasm narrow the blood vessels (mostly in hands) and increases the critical closing pressure causing the vessels to collapse
