Describe the events in cardiac cycle. Explain ’double circulation’.

Explanation

### Step-by-Step Solution

**1. Understanding the Cardiac Cycle:**
- The cardiac cycle consists of a series of events that occur during one heartbeat. It includes the contraction and relaxation of the heart chambers (atria and ventricles) and the flow of blood through the heart.

**2. Phases of the Cardiac Cycle:**
- The cardiac cycle can be divided into two main phases: diastole and systole.
- **Diastole:** This is the relaxation phase where the heart chambers fill with blood.
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