Exam 1 - Lecture 2 Flashcards
When Reynolds number is greater than _____, it means there is what?
2000; turbulent flow
what are the units for Reynolds number?
no units… it is a hypothetical number.
What is reynolds equation? What does each symbol represent?
Re = (VxDxP)/n
V = Velocity
D = Diameter
P = Density
N = Viscosity
What blood vessels are most prone to turbulent flow?
Aorta and large arteries.. closer to the heart, the more at risk.
do we see turbulent flow in the veins?
No, velocity is so low
What’s the difference between viscosity and density?
Viscosity = Thickness
Density = Mass per volume
e.g. water is more dense than oil, but oil has higher viscosity.
3 ways to assess bloodflow? (tools)
Electromagnetic detector that monitors the electric magnetic field of iron that moves with the blood.
Or an ultrasonic flowmeter and has to be implanted/wrapped around a blood vessel
lastly, a laser
How does an A-line monitor blood pressure?
Chamber in tray is a piece of metal that is pushed up and down by the pressure, giving us a blood pressure.
What is the pressure volume loop measuring?
Pressure and volume in left or right ventricle
How does the shape and scale change for left and right ventricle?
The shape will be the same and the volume will be the same, but the pressure will be different.
Phase I of pressure volume loop?
Filling, aka diastole.
Starts when mitral valve opens and ends when it closes.
The volume that the left ventricle fills at in a healthy heart?
50mL
What is the volume leftover after systole? what is it called?
50mL, end-systolic volume or ESV
Most of the filling during phase I is
passive
What is filling DEPENDENT upon?
How much preload we have/pressures entering heart
What is the atrial kick?
Last portion of filling the ventricle gets before it contracts, gets the last 10mL’s of blood into the ventricle to total 120mL’s
How much total blood fills during phase I?
70mL’s
When does the atrial kick become very important?
When heart is sick and doesnt passively fill as much.
In healthy people, its not very important.
In diseases hearts, what % is dependent upon atrial kick
greater than 25%
What does diastole mean?
filling
Phase 2 of pressure volume loop
Contraction, then ventricle pressure is greater than atrial pressure and the mitral valve closes.
What phase are both aortic valve and mitral valve closed?
Phase II and IV
What signals the beginning and end of phase II?
Mitral valve closes is the beginning, the end is when the aortic valve opens.
When is there no change in volume in the ventricle? what is it called?
Phase II and phase IV, called the isovolumetric contraction and isovolumetric relaxation.
When does phase III start?
when aortic valve opens because the ventricle pressure is greater than the aortic pressure.
What is phase III called?
Period of ejection
What is the equation of stroke volume?
difference between volume during isovolumetric contraction (beginning of phase III) and volume during isovolumetric relaxation (end of phase III)
What signals the end of Phase III?
Aortic valve closing
why does the aortic valve close?
Pressure in aorta is greater than pressure in ventricle.
What does the mitral valve need to open?
needs ventricular pressure to drop lower than the atrium.
Beginning and end of phase IV?
Aortic valve closes and then mitral valve opens
How many phases is the pressure volume loop?
4
Diastole will start when?
When the aortic valve closes, aka beginning of phase IV or end of Phase III
Systole will start when?
End of phase I, beginning of phase II.
What phases are during diastole?
end of phase III to beginning of phase II
When blood is going into the ventricle, describe the speed of the filling
rapid filling when valve first opens, then slows down, then atrial kick.
If the mitral valve is stenotic, how is the filling?
Going to fill much slower
Describe the speed of the blood ejecting out of the ventricle during systole?
Super fast at first, then slowly comes out towards the end of systole.
Blood is ejected out of the ventricle until the end of
phase III
The first heart sound is
AV valve closing
The second heart sound is
the aortic valve closing
When is aortic pressure highest?
Peak of Phase III
When is aortic pressure lowest?
Beginning of phase II
All the valves in the heart are
one way valves
The Atria do not have a valve that is
behind them
If the right atrial greater than zero, how does that affect venous return? why?
Lower venous return, because delta P of the CV system is what moves blood. This would lower the delta P.
What is the plateau of venous return? (the pressure in the atria and how much volume)
-4mmHg, about 6L/min.
What is the transitional zone for venous return?
0mmHg to -4mmHg, 5-6L/min
Why does the venous return plateau?
The large veins that fill the right atria can collapse past -4mmHg, preventing more venous return.
Mean systemic filling pressure (definition and abbreviation)
Sum total of all pressure in the cardiovascular system, which is 7mmHg. Abbreviated as Psf
what is the total delta p of PSF and right atrium?
7mmHg
What can change the Psf most effectively?
contraction of systemic veins, since they are large and contain the most blood volume
If you increase the Psf, the venous return will
increase
If our Psf is doubled to 14, the venous return would be
10L/min
If you notice, the Psf doubled and so did the venous return. THE SLOPE DID NOT CHANGE!
If our Psf is cut in half to 3.5mmHg, the venous return would be
2.5L/min
Increase or decrease in CVP should also change
Right atrial pressure
Intrathoracic pressure normally is
0mmHg
If someone has high PEEP, it will
increase intrathoracic pressure and reduce venous return to the heart cause it can collapse those veins
IF there is sympathetic stimulation, an increase in right atrial pressure to 4mmHg will result in
a great increase in cardiac output.
If there is normal sympathetic stimulation, the max cardiac output is
13l/min at +4mmHg
If there is MAX sympathetic stimulation, the max cardiac output is
23-25L/min at +4mmHg, but if youre an elite athlete it can go up to 40L/min
With paraympathetic stimulation, the cardiac output at +4mmHg in the right atria is
around 7-8L/min
Direct atrial stretch
if atrial stretches increases, we will have an increase in heart rate and contractility.
3 reasons for increase in cardiac output when increasing right atrial pressure
Frank-starling law, direct atrial stretch, bainbridge reflex
how much can the Direct atrial stretch increase heart rate?
10-15%
its built in to our electric system, it is not a result of the brain or anything.
How much can the Bainbridge reflex increase the heart rate? How does it work?
40-50%, external reflex that is sensed by heart and carried to nervous system, carried by the vagus nerve. The atria stretch out and send signal to brain stem to increase heart rate.
Decreases parasympathetic and increases sympathetic outflow.
with more sympathetic stimulation, there is more or less right atrial pressure needed?
lower/more negative
If we slow down the heart rate, the right atrial pressure will
increase
What does the cardiac output curve look like with congestive heart failure?
More 1:1 slope with pressure and output, pretty much a straight diagonal line. There right atrial pressure will be really high to get up to 5L/min of cardiac output.
High CVP in order to sustain life!!
