Question

Assertion[A]: Atria and ventricles do not contract at the same time.

Reason[R]: This time delay allows proper filling of all the 4 chambers of the heart and results in an efficient pumping of blood.

• A. A is true and R is false.
• B. R is true and A is false.
• C. Both A and R are true and R is correct explanation of A.
• D. Both A and r are true but R is not correct explanation for A.

Answer 1

The correct option is C

Both A and R are true and R is correct explanation of A.

• During a single heart beat, the atria and ventricles do not contract simultaneously. The atrial contraction occurs prior to the ventricular contraction.
• This time delay allows proper filling of all four chambers of the heart.
• The atria relaxe while they are filled with blood. Then they contract simultaneously and pump the blood to the ventricles on their respective sides.
• Then both the ventricles contract together and pump the blood to the different parts of the body.