Cardiac cycle Flashcards
- Cardiac Cycle
composed of a period of Ventricular Contraction (Systole) followed by relaxation (diastole).
- Cycle begins with Ventricular Filling
During diastole the ventricles are relaxed and blood flows in from the atria through the open AV valves. Initially, ventricular filling occurs passively because pressure in atria is greater than pressure in ventricles.
- Toward the end of Ventricular Diastole
the Atria depolarization is initiated by SA node, the atria contract, squeezing more blood through AV valves into ventricles. This is Atrial Systole. Ventricular blood volume remains constant because all cardiac valves are closed.
- Impulse generated by SA node spreads…
to AV node, continues to bundle of His, then the bundle branches and finally the Purkinje fibers.
- Result is Depolarization of ventricles known as…
Isovolumetric contraction. Ventricles begin to contract, causing intraventricular pressure to rise greater than the pressure in the atria and the AV valves to close.
- The amount of blood in the ventricles at this time is…
EDV (end diastolic Volume)
- This contraction of the ventricles, also known as…
Ventricular Systole, results in rapid rise in ventricular pressure.
- This end volumetric pressure, which is the greatest amount the ventricles can stretch is…
the preload.
- As ventricular pressure exceeds aortic or pulmonic pressure…
the semilunar valves are forced open and a period of rapid ejection occurs.
- The tension or stress developed in the left ventricle during ejection is known as…
the afterload.
- This is followed by reduced ejection as the aortic and pulmonic pressures rise and ventricular pressures and volumes fall. This is called…
Isovolumetric ventricular relaxation.
- Isovolumetric ventricular relaxation begins with semilunar valve closure in response to…
falling ventricular pressures.
- Open of the AV valves signals…
the beginning of rapid ventricular filling and the start of another cardiac cycle.
