[Exam 1] Lecture 2: Venous Return, Cardiac Output Curve, Cardiac Cycle, Pressure Volume Loops Flashcards
What is the Reynolds Equation?
What is the Reynolds number?
A hypothetical number that is completely unitless.
What Reynolds number indicates turbulent flow?
> 2,000
What is turbulent flow?
Blood moving in all different directions, with wasted energy and potential clotting risk.
Turbulent flow can also include air
What factors increase the risk for turbulent flow?
- Elevated velocity
- Wide diameter
- Higher density
In which blood vessels is turbulent flow most likely to occur?
Why?
Large arteries close to the heart, such as the Aorta.
The arterial circulation has higher velocity than venous circulation.
What is the difference between density and viscosity?
Density is mass per volume, while viscosity refers to the thickness of a fluid.
Oil is more viscous than water but water is more dense than oil.
What happens to pressure in the arterial system when volume changes?
Pressure changes a lot when volume changes a little.
How does sympathetic stimulation affect arteries and veins?
Removing sympathetic stimulation lowers pressure more in arteries than in veins.
What is a pressure-volume loop?
It represents different pressures and volumes in the chambers of the heart during the cardiac cycle.
What is the end systolic volume (ESV) in a healthy heart?
50 mls, which is the volume left in the left ventricle after the last ejection.
What primarily drives the filling of the heart during phase 1?
Passive filling, dependent on preload.
What role do the atria play in ventricular filling?
They provide a small amount of additional volume just before the heart contracts.
10 mL/s
True or False: Turbulent flow is more likely to occur in veins than in large arteries.
False.
What happens to pressure in the venous system when volume is added?
Pressure changes only a little.
What happens to pressure when sympathetic stimulation is maximized?
It can significantly increase pressure in the arteries.
What is the typical volume of blood in a healthy heart’s left ventricle at the beginning of filling?
50 mls.
What is the effect of high velocity on turbulent flow risk?
Higher velocity increases the risk of turbulent flow.
What is the total amount of blood filling during phase one of the cardiac cycle?
70ccs
Only 10ccs of that is due to the atria in healthy individuals.
120 (lvedv) - 50 (ESV)
What role do the atria play in the filling of the ventricle for healthy individuals?
Minimal role
Atria are not necessary for filling; passive flow can fill the ventricle without atrial contraction.
In patients with heart problems, how important is atrial filling?
Very important
Atrial filling becomes crucial due to potential ventricular wall thickening or chamber size reduction | In Heart Failure, as much as 25% of ventricular filling.
What is the term used to describe the contraction of the atria that contributes to ventricular filling?
Atrial kick
In healthy individuals, the atrial kick is not significant.
At what point does diastole end in the cardiac cycle?
When the ventricle starts to contract
Diastole is primarily the filling phase.
During phase two of the cardiac cycle, what happens to the heart muscles?
The heart starts to contract
This leads to increased left ventricular pressure.