Cardiac Cycle Flashcards
Systole
Contraction and emptying
Diastole
Relaxation and filling
Cardiac Output
Total volume of blood ejected by the heart per minute
Stroke Volume
Volume of blood ejected by the ventricle on each beat
Cardiac Cycle
All events from the beginning of one heart beat to the beginning of the next one.
What do we call the remaining volume in each ventricle after systole?
End systolic volume
What do we call the volume of blood within the ventricles at the end of the filling phase?
End diastolic volume
How is each cardiac cycle initiated?
Spontaneous generation of an action potential in the sinus node
Where does blood enter the heart?
Into the RIGHT atrium through the inferior and superior VENA CAVA
Into the LEFT atrium through the right and left PULMONARY veins
Once the atria push blood into the ventricles, where does it go from there?
From the RIGHT ventricle, deoxygenated blood travels through the pulmonary trunk to the LUNGS
From the LEFT ventricle, oxygenated blood is ejected into the AORTA to the rest of the body.
What is the state of the AV valves during continuous flow of blood into the atria, and during atrial contraction?
AV valves are open
What is the state of the AV valves at the beginning of ventricular systole?
When contraction begins, and ventricular pressure increases (>80mmHg), AV valves are pushed closed.
*Closing of the AV valves at the beginning of ventricular systole elicits the first heart sound (Lub)
What do chordae tendineae do?
Attach AV valves to the papillary muscles of the ventricles to prevent them folding backward into the atria during ventricular systole.
After what phase of ventricular systole do the semi-lunar valves open?
Ventricular Ejection.
Right after the AV valves close, pressure is high enough in the ventricles to open the semi-lunar valves and eject blood into the arteries.
How much of the blood within the ventricles is ejected into the arteries?
60% - Ejection Fraction
What is the state of the semi-lunar valves immediately following ventricular systole?
During early diastole, ventricular pressure decreases, semi-lunar valves close, and blood flows back from the arteries and fills the cusps.
*Closing of the semi-lunar valves following ventricular systole is the second heart sound (Dub.)
What is isovolumetric relaxation?
Phase of ventricular diastole in which the semi-lunar valves have closed and the AV valves remain closed. Relaxation with no change in blood volume in the ventricles.
In the late phase of diastole, what is the state of the AV valves?
AV valves are opened due to increased pressure in the atria. Blood is allowed to flow passively into the ventricles, filling them 70% and preparing for the next cycle.
What is isovolumetric contraction?
First phase of ventricular systole in which ventricles begin to contract, and pressure increases enough to close the AV valves, but is not yet high enough to open the semi-lunar valves. No change in blood volume.
