Heart pt 3 (1st half!) Flashcards
What is happening in the heart during late diastole?
Both sets of chambers are relaxed and passive ventricular filling is taking place.
What is happening during atrial systole?
Atrial contraction forces a small amount of additional blood into the ventricles (?)
What does EDV stand for and what is it?
End-diastolic volume is when the ventricles are filled with the maximum amount of blood; occurs at the end of ventricular relaxation.
Describe what is happening during Isovolumic ventricular contraction.
This is when the first phase of ventricular contraction pushes the AV valves close but has not yet created enough pressure to open the semilunar valves.
What is ventricular ejection?
As ventricular pressure rises and exceeds pressure in the arteries, the semilunar valves open and blood (about half the blood present) is ejected.
What does ESV stand for and what is it?
End-systolic volume: the minimum amount of blood in the ventricles. Avg: 65 mL
Describe what is happening during Isovolumic ventricle relaxation.
As ventricles relax, pressure in ventricles drops, blood flows back into cups of semilunar valves and snaps them closed.
What does the peak of the R wave on the ECG represent?
The isovolumic ventricular contraction (when the pressure builds with all valves closed).
What does the ST phase on the ECG represent?
The early phase of ejection: when the aortic valve opens as the ventricular pressure exceeds aortic pressure.
What does the T wave on the ECG represent?
The later phase of ejection when the back pressure of aorta reduces ejection.
What causes the first heart sound?
Closing of the AV valves.
What causes the second heart sound?
Closing of the semilunar valves.
What effect does slow heartbeat have atrial systole?
The pressure gradient from the atrium into ventricle is adequate to fill the ventricle; the blood is sucked into the ventricle.
What effect does tachycardia have on atrial systole?
Ventricular diastole is shorter and less blood enters the ventricle. To compensate, atrial contraction ejects blood into the ventricle to provide adequate filling: this is atrial systole.
What is represented by the passive tension curve?
Diastolic pressure
What is represented by the active contraction curve?
Systolic pressure
What is Cardiac Output?
The measure of heart performance
What is Stroke Volume? And how would you calculate it?
The volume of blood ejected in one beat (in ml).
SV= EDV (end diastolic volume) - ESV (end systolic volume). SV: the amount of blood that has left the heart, and made it to the circ. system. ESV: the blood that stays behind.
How do you calculate Cardiac Output and in what units?
CO (ml/mm) = SV stroke volume (ml) x HR heart rate (beats/min)
What is Stroke Volume determined by?
Preload (initial, i.e. end-diastolic, volume); Afterload (aortic pressure); Contractility (inotropic state).
What is the Ejection Fraction?
How much blood was ejected compared to how much is left:
SV/EDV = 75ml/150ml = 50%
Define Preload
The fiber length from which the muscle contracts (diastolic filling stretches the myocardium to the end-diastolic volume, EDV). The filling stops when the intraventricular pressure is equal to the incoming atrial venous pressure. Filling happens in two stages: passive late diastolic filling and atrial systole. (this is a dumb slide)
What is the Frank-Starling Law?
Increased preload (venous return) produces a commensurate increase in stroke volume.
True or False? Increasing diastolic filling (preload) increases the strength of the ventricle.
True. The force of ventricular contraction depends on the muscle fiber length, i.e. end-diastolic filling, the preload.
