Control of the Heart Flashcards
How does the flow move in the following diagram?
start at mitral valve opening → move right → go around
Where is the preload in this diagram?
where mitral valve closes (150 mmHg)
Where is the afterload in this diagram?
where the aortic valve opens
Where is the ESV in this diagram?
Where the mitral valve opens
What happens to pressure and volume during isovolumetric contraction?
pressure increases
volume stays the same
Calculate SV and EF using the pressure volume loop.
SV = 50
EF = 100/150 = 67%
What happens if you increase preload and everything else stays constant?
SV increases b/c of frank starling relationship
ESV stays the same
Why does increasing preload and keeping everything else constant increase SV?
b/c of Frank-Starling relationship
the more blood in the ventricle, stretching close to optimal length when it contracts it pumps out extra volume
What happens if you increase afterload and everything else remains constant?
SV decreases
Why does increasing afterload and keeping everything else constant decrease SV?
the heart has to use more energy to generate higher pressure
(heart shortens less → ejects less blood)
What happens if you increase contractility and everything else remains the same?
SV is increased at the expense of ESV (ESV is reduced)
Why does increasing contractility and keeping everything else constant increase SV but decrease ESV?
length stays the same but more calcium is released
shortens more efficiently
empty more volume
What are the effects of changes in afterload in the normal heart?
SV reduced → need higher pressure to open aortic valve
heart adapts by increasing preload →heart has to do more work to maintain SV under increased pressure → wall stress is elevated → HTN → leads to heart failure
What are the effects of changes in afterload in the failing ventricle?
pressure volume loops is shifted to the right → more volume in ventricle → operating at more length with high volume
increased afterload on failing ventricle → pressure volume loop reduced → SV decreased
The opening of the mitral valve occurs at the beginning of which phase of the cardiac cycle?
rapid filling
Using the figure, which of the following best describes AB in the ventricular pressure-volume loop?
A. isovolumic relaxation
B. rapid ejection
C. rapid filling
D. isovolumic contraction
E. SV
Isovolumic contraction
Using the figure, what is the ejection fraction?
EF = SV/EDV
EF = (100-40)/100 = 60%
