Venous System Flashcards
Why does the venous system serve as a reservoir of blood?
By the time blood reaches the venous system it has lost most of its energy and is thinner/more compliant allowing for large volume of blood
What is the structural differences allowing for veins to be a reservoir of blood?
At large volumes when veins become resistant to more blood due to collagen, sympathetic stimulation causes the smooth muscle to pull on collagen fibers decreases the maximal diameter of the vein.
What is venous return?
The blood traveling from the veins back to the heart to be pumped back into circulation again
How does gravity effect venous return?
It is harder for the veins to “pump” blood back to the heart against gravity since it have very low pressure. When standing, large volumes of blood drop out of ventral venous compartment and into legs causing a loss of preload and CO falls. HR will raise in an attempt to restore CO (orthostatic reflex)
What is mean systemic pressure and how can it be altered?
When the pump is off the pressures in the arterial and venous systems are equal and depend on blood volume and vessel compliance of the entire system
standard value is 7!
what are the coping mechanisms against gravity?
Skeletal muscle pump
sympathetic stimulation - (more of a sucking then pumping)
increase vol of the whole system - more to chronic settings
What does the cardiac function curve describe?
The effect of CVP on cardiac output
What is the guyton curve?
both the pump and the vasculature work together and describe parts of the same system.
What is the equillibrium point
defines the relationship between cardiac and vascular function.
How can the cardiac function curve be altered?
Changing the inotropic state, increased sympathetic nervous system input
How can vascular function curve be altered?
Increases in blood or plasma volume with an increase in MCP, and differences in arteriolar resistance with no MCP change
What does inspiration cause?
increased preload and stroke volume in right heart and decreased in the left heart
What does exhalation cuase?
increased preload and SV in the left heart and decreased in the right heart
What is valsalva maneuver?
Straining against a closed glottis
