Difference Between Systole and Diastole

Systole vs Diastole
 

The cardiac cycle of animals is composed of a systole and a diastole of the atria, and a systole and a diastole of the ventricles. During the cardiac cycle, two atria contract at the same time, and while they are relaxing, two ventricles start to contract simultaneously. Here, the contraction phase is called systole, whereas the relaxation phase is called diastole. If the terms systole and diastole are used alone, it usually refers to the action of the ventricles. Usually with a heart rate of 75 beats per minute, one cardiac cycle takes 0.8 second to complete.

Difference Between Systole and Diastole

 

Diastole

Diastole is the relaxation phase of the atria and ventricles. It occurs after the subsequent repolarization of the cardiac muscles. Diastole occurs followed by the atrial and ventricular systole and remains for 0.4 seconds. During the ventricular systole, atria are in diastole and get blood through the venae cavae and pulmonary veins. 70% of the blood enters to ventricles during the diastole while the remaining 30% enters during the atrial systole.

Systole

Systole is the contraction phase of atria and ventricles. It occurs due to the spreading of excitation across the heart. The action of atria contraction is called the atrial systole, whereas that of ventricle contraction is called the ventricular systole. During the atrial systole, the blood in the atria is forced into ventricles through atrioventricular valves. Atrial systole normally lasts for 0.1 second. While atria are contracting, the ventricles are in diastole. The duration of ventricular systole is about 0.3 second. During the ventricular systole, the pressure increases inside the ventricles. This closed atrioventricular valves and the opened semilunar valves, allowing blood enter into the pulmonary trunk and ascending aorta, carry blood away from the heart.

What is the difference between Systole and Diastole?

• Systole is the contraction phase of atria and ventricle, whereas diastole is their relaxation phase.

• Systole occurs due the spread of excitations, whereas relaxation occurs due to the subsequent repolarization of the cardiac muscle.

• While atria are in systole, the ventricles are in diastole, and vice versa.

• Generally, aria systole lasts for about 0.1 second while atrial diastole lasts for the remaining 0.7 second.

• Ventricular systole lasts for about 0.3 second while ventricular diastole lasts for the remaining 0.5 second.

• Atrial systole is followed by ventricular systole, whereas four chambers are then simultaneously in diastole for one half of the cycle.

 

Read more:

1. Difference Between Systolic and Diastolic Pressure

2. Difference Between Systolic and Diastolic Heart Failure