Question

Blood enters the heart because muscles of the

• A. Atrium contracts
• B. Atrium relaxes
• C. Ventricle relaxes
• D. Ventricle, contracts

Answer 1

The correct option is B Atrium relaxes

B. Atrium relaxes

Reason: During a heartbeat there is contraction and relaxation of atria and ventricles. The contraction phase is called the systole while the relaxation phase is called the diastole. Atrial diastole is characterized by the relaxation of the atrial muscles. During this stage, the blood enters into the atria, as the volume of the blood in the atria increases the pressure within it decreases.