The contraction of heart is called ........... while the relaxation of heart is called …………… .

Explanation

### Step-by-Step Solution:

1. **Understanding Heart Function**: The heart has two primary phases in its cycle: contraction and relaxation. These phases are essential for the heart to pump blood effectively throughout the body.

2. **Identifying Contraction**: The phase where the heart muscle contracts and pumps blood out of the heart is referred to as **systole**. During systole, the ventricles contract, pushing blood into the arteries.

3. **Identifying Relaxation**: The phase where the heart muscle relaxes after contraction is called **diastole**. During diastole, the heart chambers fill with blood as the heart prepares for the next contraction.

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