Vascular Control I & II Flashcards
The cardiovascular system is a ______ system.
closed
Blood input should ____ output or in other words venous return should _____ cardiac output (since this is a closed system) in a steady state. These both have the units of _______. For instance, is cardiac output increases during a marathon, venous return must ______ also.
Blood input should equal output or in other words venous return should equal cardiac output (since this is a closed system) in a steady state. These both have the units of volume/min. For instance, is cardiac output increases during a marathon, venous return must increase also.
So on graphs, when I see venous return, think Cardiac Output.
Describe cardiac preload & afterload
Preload is the pressure due to the amount of stretch at the end of inflow in the ventricle (starlings law). It is determined by ventricular end diastolic volume. Preload is directly proportional to stroke volume. Preload = central venous pressure.
Afterload is the pressure needed to be generated by the ventricle to eject blood. It is the end systolic ventricular pressure
What is the function of the arterioles in the body?
They determine systemic vascular resistance (they have the highest resistance) & afterload.
What is the function of the capillaries in the body?
Diffusion of nutrients, O2, ATP, glucose, etc.
What is the function of the venous 2 compartments in the body?
1) The central venous compartment determines preload.
2) The peripheral venous compartment holds the most blood, due to its increased compliance.
Functionally, you can think of them as 2 diff systems because if pressure is greater in one of them, flow will follow in that direction.
The function of arteries is to act as ______ for the blood.
conduits
The central venous compartment consists of
the heart.
Whatever comes into the central venous compartment, must come out as CO.
The peripheral venous compartment consists of
venous system after the capillaries & before the heart
If the heart is not beating, most of the blood will _______ in the venous circulation, due to its _____ compliance.
pool
increased
Right atrial pressure is the same as
central venous pressure
Jugular venous pressure from the _______ can help us determine ______. If jugular venous pressure is high then ____ & ____ is also high.
external jugular
preload & central venous pressure
central venous pressure
left ventricular end diastolic volume & pressure
It is preferable to examine the internal rather than external jugular veins since the internal jugular veins are in a direct line with the superior vena cava and right atrium whereas the external jugular veins are not in a direct line with the superior vena cava and connect with it after negotiating two almost 90 degree angles
If you are hypotensive, the jugular veins will be
flat & non-distende–since the barometer (external jugular) is low
Central venous catheters can get central venous pressure also via the internal jugular (medicine can be given through it too).
If the central venous pressure is equal to the peripheral venous pressure, what would happen?
No flow would occur due to no pressure gradient
What are the typical pressures in the central & peripheral venous compartments? With these values, what is the venous return?
Peripheral = 7mmHg
Central = 0mmHg
venous return = 7 L/min (from graph)
- See pg. 8
Mean arterial pressure or MAP is typically?
100 mmHg
If we stop someones heart, their MAP will _______ 0mmHg because _________. Therefore the MAP will be ________.
not equal
there is a reservoir of blood in the veins (& other vessels) giving a BP
7mmHg due to the peripheral venous pressure being this value = mean systemic filling pressure
1) Define mean systemic filling pressure.
2) Therefore, if I remove blood from a patient, their mean systemic filling pressure will _______. Conversely, if I give them blood their mean systemic filling pressure will _______, even if their heart is not beating.
1) The pressure that is exerted by the total body volume that is in the circulatory system. Mean systemic filling pressure is defined as the pressure in the blood vessels during cardiac arrest. It is an important determinant for venous return to the heart and thus for cardiac output.
2) Therefore, if I remove blood from a patient, their mean systemic filling pressure will decrease. Conversely, if I give them blood their mean systemic filling pressure will increase, even if their heart is not beating.
If we decreased a patient’s central venous pressure (by taking blood from their peripheral venous compartment) to 4 mmHg, what would happen? How would the curve initially shift?
NOTE: by taking blood from the peripheral venous compartment there is a decrease in the pressure gradient into the central venous compartment. Therefore, the flow & venous return decreases.
The venous return would initially decrease & shift the curve left because the peripheral venous compartment pressure would decrease. If the X axis decreases so does the y axis.
See pg. 9
If you are losing blood, the body will adjust by _______ venous tone, which increases venous return to the heart & it will shift the curve _____.
increasing
right
See pg. 9
If you increase the blood volume or venous tone on the curve on pg. 9 the curve shifts _____, & if you decrease blood volume or venous tone you shift it to the _____.
If you increase the blood volume or venous tone on the curve on pg. 9 the curve shifts right, & if you decrease blood volume or venous tone you shift it to the left.
The arterioles regulate the circulatory system & the ______ circulation.
The arterioles regulate the circulatory system & the venous circulation.
Arteriolar vasoconstriction ______ venous return & arteriolar vasodilatation ______ venous return with ______ in mean systemic filling pressure. If you _____ your arterioles, you increase stroke volume.
decreases
increases
no change
vasodilate
Mean systemic filling pressure does not change in vasodilation or vasoconstriction because it is only shifting or redistributing blood & no blood is being lost. Mean systemic filling pressure only changes when there is an increase or decrease in blood volume. Therefore, if I remove blood from a patient, their mean systemic filling pressure will decrease.
The units for CO & venous return are
liters/ min, since it is a flow
1) Stroke volume =
2) If you increase end systolic volume, what happens to stroke volume
end diastolic volume - end systolic volume
1) SV = EDV - ESV
2) it decreases
If you vasodilate the arterioles, it is _____ for the left ventricle to pump against the new lower resistance so the ESV ______ & afterload _______. Therefore, stroke volume ______ & cardiac output ______.
If you vasodilate the arterioles, it is easier for the left ventricle to pump against the new lower resistance so the ESV decreases & afterload decreases. Therefore, stroke volume increases & cardiac output increases.
SV = EDV - ESV
CO = HR x SV
Afterload is the pressure needed to be generated by the ventricle to eject blood. It is the end systolic ventricular pressure
see pg. 14
Arteriolar vasoconstriction or vasodilation _______ change peripheral venous compartment volume or Mean systemic filling pressure since ______.
does not
Mean systemic filling pressure = peripheral venous compartment
Describe the Frank Starling curve
If you increase filling pressure & stretch the myocytes, you have greater cardiac output. In other words, if preload is high, you have a greater stroke volume & cardiac output.
See figure on pg. 10
Describe the equillibrium point between the Starling curve & the venous function curve: It is the equilibrium that the body goes to so that cardiac output or venous return is _____ & @ rest, central venous pressure is ______.
It is the equilibrium that the body goes to so that cardiac output or venous return is 5 L/min & @ rest, central venous pressure is 2mmHg.
See figure on pg. 10
Increased contractility via sympathetic activity (norepi) shifts the starling curve ______ & decreased contractility shifts the starling curve to the _____.
left & up
right & down
See figure on pg. 11
If someone has an MI, the Starling or normal cardiac function curve shifts ____.
right & down
A person with heart failure’s cardiac output will decrease to shift down
To keep central venous pressure, the curve will also shift right. They try to increase venous return to increase cardiac output.
See figure on pg. 10 & starling curve in problems folder
Analyze figure on pg. 11
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Dr Dhamoon has been called in for an emergency and WILL NOT be presenting his lecture at 9am today. This lecture is officially CANCELLED. As a consequence, we will limit the number of unit exam questions for Vascular Control I&II to a total of 2 only (not 4).
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