12.1 A Flashcards
What controls the opening of heart valves?
they open passively in response to pressure gradients between different chambers of the heart
Describe the resistance of heart valves and the pressure differential needed to open them?
they provide very little resistance, thus very small pressure differentials are sufficient to open them
Ventricular systole begins with what event?
mitral valve closure
Ventricular systole ends with what event?
aortic valve closure
What are EDV and ESV?
end diastolic volume and end systolic volume describe the blood volume in the ventricle at two specific time points
EDV - ESV equals what?
stroke volume
How does stroke volume relate to EDV?
SV = EDV - ESV
The ventricular pressure at the time of aortic valve opening is roughly what?
80 mm Hg
The ventricular pressure at the time of aortic valve closure is roughly what?
115 mm Hg
What is the equation for ejection fraction?
stroke volume/EDV
What is the normal range for ejection fraction?
0.5 to 0.7
Ejection fraction is an index of what?
contractility of the heart
While diastolic dysfunction is due to impaired filling, systolic dysfunction is due to impaired what?
impaired force generation
What happens to the ejection fraction in an individual experiencing diastolic dysfunction?
there is no change, ejection fraction only decreases in systolic dysfunction
Describe the rate of ventricular filling during diastole?
it fills rapidly and then the rate begins to slow
Most of ventricular filling is due to what?
the pressure gradient more so than atrial contracture
Atrial contraction becomes more important to ventricular filling as what occurs?
as heart rate increases and the time for passive filling decreases such as occurs during exercise
What is isovolumic ventricular contraction?
the time during which the ventricle is contracting but all the valves are closed, so the volume goes unchanged and the pressure builds
Ventricular ejection begins when what occurs?
the ventricular pressure rises above aortic pressure, opening the aortic valve
Why does the rate of ventricular ejection decline over the course of each ejection?
- volume decrease during ejection means the pressure decreases
- repolarization begins so contractile force decreases
What happens to aortic pressure during ventricular contraction?
it increases and then slightly decreases following ventricular pressure until the aortic valve closes at which point it remains higher than ventricular pressure due to the elasticity of the aorta
Ventricular relaxation is said to be _____.
isovolumic
What are the two phases of diastole?
isovolumic relaxation and ventricular filling
What are the two phases of systole?
isovolumic contraction and ventricular ejection
Although the two sides of the heart are in series, the SV does not have to be equal during each beat, what must be equal is…
the average SV over time
How does the peak systolic pressure in the right ventricle compare to that of the left ventricle?
it is roughly 1/5 the pressure of the left
Why does the mitral valve close slightly before the tricuspid valve?
because the left ventricle has a thicker wall, pressure rises faster in the left ventricle than in the right
Which opens slightly earlier, the pulmonic or aortic valve?
the pulmonic valve opens slightly before the aortic during systole because the aortic pressure is greater than that of the pulmonic system
Which closes earlier during diastole, the pulmonic or aortic valve?
the pulmonic valve
What happens to arterial pressure during ejection?
it increases
