Flashcards in L2. Vascular Function and its Control Deck (13):
Where does the majority of the blood volume reside in the body?
Up to 65% of the body's blood volume lives in the systemic venous system.
Compare the compliance of the arterial and the venous system
The venous system has much more compliance than the arterial system, it holds more blood.
The venous side is the volume reserve pool while the systemic is the pressure reserve pool (it is much more sensitive to pressures than the venous side).
Why is it detrimental to have high pressures in the venous circulation?
High venous pressure would mean that the pressure gradient throughout the body would dissipate making one way flow back to the heart very difficult.
What does the term autotransfusion mean?
Autotransfusion is the compensatory mechanism of the venous system where a decrease in arterial blood and pressure causes venous blood reserves to increase the venous return to compensate for decreased CO.
What is the consequence of venoconstriction?
Increase in venous pressure, increased venous return (by increasing the pressure gradient and increasing atrial filling), increases EDV and SV which increases CO thereby increasing Pressure in the systemic circulation
What is the mean arterial filling pressure? What factors affect the magnitude of MAFP?
This is the pressure found if the CO was zero (and blood was allowed to settle and distribute around the body). It is approximatley 7 mmHg.
It depends on the compliance of the vessels in the body and the total blood volume.
What happens to the venous blood volume when you reduce TPR?
Reduced TPR = More blood in the tissues = less blood in the arterial system and more blood in the venous system.
Describe the vascular-function curve
Describes how changes in CO cause a change in venous pressure. Flow of blood sets up pressure gradients across the system (doesn't change total blood volume). And blood flows out of the central veins and into the heart through pressure gradients set by the heart. And with blood going into the systemic systems pulled out from the venous system there is a rise on systemic pressure and a decrease in central venous pressure.
Decreasing the central venous pressure means that the venous return would increase due to the higher gradient formed (this increases CO).
Why is increasing blood volume equivalent to venoconstriction in terms of the vascular function curve?
Because increasing venoconstriction means that there is an increase in pressure within the veins. This is the same consequence if you increased the blood in the veins.
What happens to the vascular-function curve if you increased blood volume (or venoconstriction)
More blood = higher MCFP
And for every given CO there is more central venous pressure (shifts the curve up)
What happens to the vascular function curve if you decrease TPR?
Decreasing TPR decreases the volume of blood in the veins and decreases the central venous pressure and thus for every CO, the central venous pressure is less. (The MCFP doesn't change)
Describe the cardiac function curve
The cardiac function curve describes how changes in venous pressure affect the CO. Increasing the pressure in the veins increases