Question

Filling of atria and ventricles begin respectively during X and Y phases of cardiac cycle.
1.) X - Atrial systole ; Y- ventricular systole
2.) X - ventricular systole y-cardiac diastole
3. X - cardiac diastole ; r - Atrial systole
4) X- ventricular diastole; Y - Atrial systole​

Answer 1

(3) option is correct,

becozzzzzz at the time of cardiac diastole blood is filled in all chambers of heart simultaneously including the atria and when atria perform systol then blood moves in ventricle(rapidly).....

Hope this help u!!!!!!!!

Answer 2

Answer: 3. X - cardiac diastole ; r - Atrial systole

Explanation:  

• Cardiac diastole (or more accurately auricle diastole) - In this period both auricles are relaxed and filled with blood.
• Atrial systole - In this period both auricles are contract and 25-30% blood flows from auricle to ventricle.

Sequential changes are occur inside heart during each heart beat is known as cardiac cycle.

Duration = 60/72 = 0.8 sec

which is divided into 3 phase given in diagram -