Heart Lecture 9: Coupling of the Heart and the Peripheral Vasculature Flashcards
What happens to the amount of blood in the central venous pool when you take a deep breath?
Increases the blood to the right atrium
As central venous pressure increases, cardiac output __________
decreases (at 7mmHg, cardiac output is zero)
As CVP decreases, cardiac output ______________
increases
What is the mean circulatory pressure (Pmc)?
When central venous pressure is the SAME as peripheral venous pressure
What two factors influence Pmc?
1) volume
2) venous tone
What three things increase when venous return increases?
1) cardiac output
2) stroke volume
3) end diastolic volume
How does venous return increase or decrease?
the pressure gradient is altered between peripheral and central venous pressure
What four factors can increase the peripheral venous pressure?
1) increased sympathetic venoconstriction
2) increased blood volume
3) increased skeletal leg muscle pumping activity
4) cardiac contraction
What two factors can decrease central venous pressure?
1) increased respiratory pump activity
2) cardiac suction
Venoconstriction increases venous return by __________ compliance of veins which makes for a stiffer pipe
decreasing
Sympathetic nerve activity has what effect on venous blood flow?
constricts it thereby increasing venous return
What is normal CVP and cardiac output?
CVP: 2mmHg
Cardiac output: 5L/min
What are two scenarios that can lead to a decrease in central venous pressure?
1) cardiac output increases (takes more blood from the pool)
2) hemorrhaging (bleeding internally)
How does cardiac output respond to a sudden increase in CVP?
it acutely increases but that then causes a reduction in CVP
What does a transfusion graph look like compared to a control on the CVP vs. cardiac output graph?
It parallels the control line but the fullness of the system is increased (more volume in circulation) thereby increasing CVP
What does a hemorrhage graph look like compared to a control on the CVP vs cardiac output graph?
It parallels the control line but the fullness of the system is DECREASED
Does a hemorrhage or transfusion change the mean systemic circulatory pressure?
YES
hemorrhage –> decreases Pmc
transfusion –> increases Pmc
What are the only two factors that influence venous function?
1) Blood volume
2) Venous tone
What do an increase in blood volume and an increase in venous tone do to venous return?
INCREASES it
What happens to blood volume and venous tone when venous return decreases?
they both decrease
What factors influence the level of cardiac function?
1) sympathetic stimulation
2) inotropic (contractility) drugs
3) heart failure (depresses cardiac function curve)
How does CVP respond to a sharp increase in cardiac output (as a result of sympathetic stimulation)?
Acutely decreases since that increase in cardiac output pulls more blood out of the central venous pool
How does heart failure affect the cardiac function curve?
shifts it down and to the right (decreases cardiac output and increases CVP)
What happens to vein diameter in response to hemorrhage?
DECREASES (venoconstricts) to get more blood back to the central venous pool faster to help save cardiac output a little bit (that also increases CVP)
What sector of the autonomic nervous system kicks in during times of hemorrhage?
SYMPATHETIC –> increases contractility of the heart helping to save cardiac output a bit
What is responsible for maintaining the pressure gradient between peripheral and central venous pools in the face of gravitation forces?
Venous valves
What generates venous pressure?
cardiac contraction
