SYSTOLE AND DIASTOLE PHASES IN TH HEART

Systole means the contracted phase whereas Diastole means the relaxed phase. In heart, it starts with the contraction of the upper two auricles (known as auricular systole) meanwhile relaxation of the lower two ventricles (known as ventricular diastole), followed by contraction of the lower two ventricles (known as ventricular systole) meanwhile relaxation of the upper two auricles (known as auricular diastole).
Here, we are discussing briefly about the events that takes place while auricular systole and ventricular systole.

AURICULAR SYSTOLE AND VENTRICULAR DIASTOLE:

• Auricular muscles contract.
• Opening of vena cava vessels and pulmonary vein close.
• Blood enters ventricles by crossing through tricuspid and bicuspid valves.
• Semilunar valves at the root of the pulmonary artery and aorta are closed to prevent flow of blood back into ventricles.

VENTRICULAR SYSTOLE AND AURICULAR DIASTOLE:

• Ventricular muscles contract.
• Tricuspid and bicuspid valves close with a jerking sound.
• Blood passes into aorta and pulmonary artery through semilunar valves.
• Atria draw in blood through the opening of vena cava and pulmonary vein. 

THE HEART SOUNDS - "LUBB" and "DUP"

• The first sound "LUBB" is produced when the tricuspid and bicuspid valves get closed sharply at the start of ventricular systole.
• The second sound "DUP" is produced at the starting of ventricular diastole when the semilunar valves present at the roots of aorta and pulmonary artery get closed sharply.

THE HEART BEAT