Systemic Circulation Flashcards
Which has more volume of blood: veins or arteries?
Veins
Where are the pressures higher: veins or arteries?
Arteries
Where is compliance higher: veins or arteries?
Veins
What is the major resistance vessel?
Arterioles
Which vessels have the highest pressure drop?
Arterioles
*****
What is compliance?
Compliance is the ability of a vessel to expand or give way to stress
How do we determine the pressure in blood vessels?
Not calculation
The volume of blood in the vessel and the compliance of the vessel
How do you calculate compliance in a vessel?
C= 🔺V
———
🔺P
(delta V over delta P)
Does compliance increase or decrease with age?
Decrease
What is the transfer of blood from the arteries to the venous circulation during diastole called?
Peripheral runoff
What is the peak pressure in the arteries?
The systolic pressure
What is the pressure in the arteries just prior to ventricular ejection?
Diastolic pressure
How do you calculate pulse pressure?
Systolic Pressure-diastolic pressure
How do you calculate MAP?
MAP= DP + 1/3 PP
Approximately
What does the elastic recoil of the arterial walls do?
Converts the stored energy into capillary flow during diastole
Is flow through the capillaries pulsatile/cyclical?
No, it is pretty constant.
This is due to the elastic recoil of the arterial walls during diastole
What maintains blood flow during diastole?
The elastic recoil of the aorta and large arteries
Why do we substitute MAP for the 🔺P?
Because 🔺P represents MAP-RAP, and we assume that the pressure in the right atrium is pretty much 0
At a constant compliance, what happens to aortic pulse pressure and systolic pressure if you increase stroke volume
Increase
If you increase compliance, what happens to pulse pressure and systolic pressure?
They decrease
What happens to diastolic pressure if HR increases? Why?
Diastolic pressure increases, because there is less time between beats for the blood to “run off”
What will happen to diastolic pressure if you increase TPR/
Diastolic pressure will rise becasue there is more resistance, and less blood will “run off” between beats
Does PP increase when you decrease HR? (Remember DP drops when you decrease HR.)
What would happen to PP if you decreased HR and ALSO increased the SV?
PP will not really increase if you decrease HR only.
If you increase SV and also decrease HR, PP will increase
What happens to SP if you decrease compliance?
Increases
What is stressed and unstressed blood?
Stressed= atrial
Unstressed= venous
Where is most of your blood: venous or arterial system?
Venous (up to 70%)
Can veins contract?
Yes, they have smooth muscle in their walls
What are the pressures like in the veins?
Very low pressure 10 mmHg or less usually
What happens to the amount of unstressed blood if venomotor tone increases?
The amount of unstressed blood decreases
-the veins contracting would cause decreased venous compliance, and therefore, less blood would be in the veins and would then have to be in the arteries
Remeber, unstressed blood=blood in the veins
Stressed blood=blood in the arteries
What happens to the volume of unstressed blood if venomotor tone decreases?
Unstressed volume will increase
More blood will be in the venous/unstressed side since the compliance will increase
Are venous return and CO ever different?
No venous return and CO are always equal
It’s a closed system duh
If you alter CO, what will happen to venous return?
It will be altered in the same way
Why does an increase in right atrial pressure decrease atrial filling?
Because the filling of the R atria is due to the pressure difference between the vena cavae and the atrium, and if you increase RAP, 🔺P will decrease= less filling
As RAP increases, what happens to CO?
CO increases (Due to increased ventricular filling=increased preload)
What is the mean systemic pressure?
It is the pressure that would be there if the heart was stopped and the blood volume equalized in all spaces
If you increase the contractility/inotropicity of the heart by giving something like Digitalis, it will increase CO. How will the venous return respond, and therefore the RAP?
Venous return will also increase
RAP will DECREASE** (this is because more blood is ejected from the heart with each beat, so pressure in the R atrium will decrease)
What will happen to RAP and venous return if you decrease cardiac inotropicity/contractility?
CO will decrease, so venous return will also decrease.
RAP will increase, since there is less blood being ejected from the heart with each beat***
What happens to mean systemic pressure if you increase blood volume through a blood transfusion?
Increases
Would a decrease in venous compliance have the same effect on mean systemic pressure as a blood transfusion?
Yes it would increase
What will happen to RAP and Mean Systemic pressure if you increase blood volume?
RAP increases
Mean systemic pressure increases
What will happen to CO and RAP if you increase blood volume
Both will increase
What will happen to venous return if you decrease venous compliance (e.g., constriction of veins)
It will increase**
What are the only two things that mean systemic pressure is dependent on?
Volume
Compliance
(I think)
