It is the Succession of coordinating events taking place in heart during each beat.
The cardiac cycle takes 0.8 sec to complete a pump.
Each heart beat consist of 2 major periods.
In systole heart pumps the blood to the arteries to all part of the body
In diastole the heart gets relax and heart gets filled in the heart from all the parts of the body.
Events of cardiac cycle:-
1) ATRIAL EVENT
– ATRIAL SYSTOL. -:0.1 SEC
-ATRIAL DIASTOLE. -: 0.7 SEC
-VENTRICULAR SYSTOL. -:0.3 SEC
a) ISOMETRIC CONTRACTION
– VENTRICULAR DIASTOLE. -: 0.5 SEC
c)RAPID FILLING PHASE
d)LAST RAPID FILLING PHASE.
Explanation for all the phases:-
Starting with atrial event
– Atrial systole is also called as last rapid filling phase which is the last phase of the ventricular diastole
-10% of the blood is pushed into ventricle
-It last for 0.1 sec
– here the blood gets pushed from the atrial to the ventricle
– During contraction of the atrial the intra atrial pressure gets increased and the volume gets decrease
-Atrial systole creates the 4th heart sound which is abnormal.
– It occurs after the atrial diastole
-during these phase the ventricular systole starts simultaneously
-here the atria gets filled with blood from inferior vena cava (IVC) and superior vena cava(SVC) in the right atria and the left atria is filled with pulmonary veins.
Due to the relaxation of the atria the intra articular pressure gets decreased and volume increase.
Now after atrial event ventricular events gets started simultaneously.
a) ISOMETRIC CONTRACTION
-It is the first phase of the ventricular systole
-The tension of the muscle increases as the length of the muscle remains the same
– during the contraction the atrioventricular valve gets closed
– It produce the 1st heart sound which is normal.
-During these period the semilunar valves gets opened
-Blood is ejected out from both the vessels.
It is again divided into two
A) Rapid Ejection Period
– during the opening of the semilunar valve a large amount of blood is ejected through the vessels.
B) Slow Ejection Period
– the remaining blood in the ventricular gets ejected with a less force.
2) VENTRICULAR DIASTOLE
a) PROTODIASTOLIC PHASE
-It is the first phase if the ventricular diastole.
-As the volume of the ventricle increases the intra ventricular pressure gets decrease.
– semilunar values are closed during the phase.
– the closure of semilunar value produce the second heart sound.
-Muscular relaxation decrease in tension without any change in length of muscle.
– Here both the ventricle are relaxed.
-Intra ventricular pressure is decrease during the period.
– During the relaxation of the ventricle the Atrioventricular value gets open.
C). RAPID FILLING PHASE
-Here the blood rushes to the ventricle from the atria due to the opening of the AV valve.
-It is the first rapid filling phase .
– Almost 70% of the blood is pushed to ventricle during these phase.
-Rushing of blood produce the 3rd heart sound which is abnormal.
d) SLOW FILLING PHASE
-In these phase the ventricle filling becomes slow .
-almost 20% of the blood is pushed into the ventricle.
e) LAST RAPID PHASE
-It occurs due to atrial systole.
-when the atria contracts the blood gets pushed into the ventricles.
-almost remaining 10% of the blood is pushed to the ventricle.
– the atria gets contract simultaneously.
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