CARDIAC CYCLE

CARDIAC CYCLE:

VARIOUS EVENT OCCUR IN HEART DURING ONE HEARTBEAT ARE REPEATED IN THE SAME CYCLICAL ORDER DURING NEXT HEARTBEAT. THIS CYCLICAL REPETATION OF VARIOUS HEARTS EVENT CONSTITUTE CARDIAC CYCLE

  EVENTS IN CARDIAC CYCLE

1-SYSTOLE(CONTRACTION OF HEART CHAMBER)

2-DIASTOLE(RELAXATION OF HEART CHAMBER)

CARDIAC CYCLE TIMING

 NORMALLY THE HEART BEAT RATE IS 75 TIMES PER MINUTE

CARDIAC CYCLE IS 0.8s

1-ATRIAL SYSTOLE IS 0.1s

2-ATRIAL DIASTOLE IS 0.7s

3-VENTRICAL SYSTOLE IS 0.3s

4-VENTRICULAR DIASTOLE IS 0.5s

5-JOINT DIASTOLE IS 0.4s

    IN START ATRIA CONTRACT FOR 0.1s WHEN ATRIA RELAX IN THE SAME TIME VENTRICES CONTRACT. WHEN VENTRICULAR SYSTOLE COMPLETED IN THE SAME TIME 0.3s OF ATRIAL DIASTOLE ALSO COMPLETED. NOW VENTRICLE GOING TO RELAX FOR 0.5s IN THE SAME TIME 0.4s OF ATRIAL RELAXATION ALSO REMAIN SO WE SAY THAT FOR 0.4s BOTH ATRIA AND VENTRICLES ARE IN RELAXED PHASE THIS PHASE OF 0.4s IS KNOWN AS 

JOINT DIASTOLE

  ATRIAL SYSTOLE

 SA NODE DISCHARGES IMPULSE WHICH RESULT IN CONTRACTION OF ATRIA. ATRIAL DEPOLARIZATION FORM P-WAVE IN E.C.G. ATRIAL SYSTOLE CONTRIBUTE 25 ML OF BLOOD TO EACH VENTRICLE(WHICH ALREADY CONTAIN 105 ml OF BLOOD)

WHEN PRESSURE IN VENTRICLES BECOME ENOUGH TO OPEN SEMILUNAR VALVE THEN 70 ml OF BLOOD IS EJECTED FROM EACH VENTRICLE. THIS IS CALLED STROKE VOLUME. AT THE END OF VENTRICULAR SYSTOLE 60ml OF BLOOD IS PRESENT IN EACH VENTRICLE. THIS IS CALLED END SYSTOLIC VOLUME. THIS 60 ml CHANGE TO 105 IN JOINT DIASTOLE

Atria are considered as extension of great vessel

   Source of data:from unacademy lactures. I listen lacture about cardiac cycle and important points note down.