Question

give short description of each phase of the cardicac cycle

where is blood going to and from?

b. does a valve open or close at the beginning or end of the phase?

c. what does volume in the ventricles look like? (eg: getting higher, same, getting lower)

d. Are the ventricles contracting or relaxing?

Answer 1

THE CARDIAC CYCLE IS A SERIES OF PRESSURE CHANGES THAT TAKE PLACE WITHIN HEART .THESE PRESSURE CHANGES RESULT IN MOVEMENT OF BLOOD THROUGH DIFFERENT CHAMBERS

IT HAS 4 MAJOR STAGES

1 ATRIAL SYSTOLE

CONTRACTION OF ATRIA DUE TO ACTION POTENTIAL FROM SA NODE .IT FORCES THE BLOOD TO FLOW IN TO LOWER CHAMBERS OR VENTRICLES BY THE OPENING OF BICUSPID AND TRICUSPID VALVES

2 VENTRICULAR DIASTOLE

DURING THIS PHASE VENTRICLE FILLED WITH BLOOD ,NO CHANGE IN VOLUME OF BLOOD BUT A PRECIPITOUS FALL IN VENTRICULAR PRESSSURE KNOWN AS ISOVOLUMETRIC RELAXATION

.EVENTUALLY VENTRICULAR PRESSURE BECOME LOWER THAN ATRIAL AND AV VALVES OPEN CAUSE FILLING OF BLOOD IN VENTRICLES KNOWN AS RAPID FILLING PHASE  

THE VOLUME OF BLOOD PRESENT IN THE VENTRICLE AT THE END OF DIASTOLE IS CALLED ENT DIASTOLIC VOLUME OR PRELOAD

3 VENTRICULAR SYSTOLE

CONTRACTION OF VENTRICLE . AS IT CONTRACTS THE PRESSURE INCREASES RESULTING IN CLOSURE OF AV VALVE BUT THE PRESSURE NOT SUFFICIENT TO OPEN SEMILUNAR VALVES THIS STAGE IS KNOWN AS ISOVOLUMIC CONTRACTION

THE PRESSURE FURTHER INCREASES AND SEMILUNAR VALVE OPENS ALLOW THE BLOOD TO PASS IN TO AORTA FROM LEFT VENTRICLE AND PULMONARY ARTERY FROM RIGHT VENTRICLE . THIS PHASE IS EJECTION PHASE

THE AMOUNT OF BLOOD EJECTED IS KNOWN AS STROKE VOLUME THE AMOUNT OF BLOOD LEFT IN VENTRICLE AFTER A CONTRACTION IS AFTERLOAD OR END SYSTOLIC VOLUME

4 ATRIAL DIASTOLE  

RELAXATION OF ATRIA WHILE VENRICLE CONTRACTION TAKEPLACE

B THE VALVES OPENS NOT INITIALLY BUT WHEN THE PRESSURE INCREASES IN ONE CHAMBER AND IT EXCEEDS THAN OTHER ONE

C STROKE VOLUME WILL BE 70 TO 80 ML . WHEN VENTRICULAR SYSTOL BEGINS THE VOLUME IS 130ML

THERE IS A RESIDUAL VOLUME OF 50 TO 60 ML AFTER EVERY CONTRACTION

D VENTRICLE HAS BOTH STAGES A DIASTOLIC AND SYSTOLIC STAGE