The cardiac cycle includes all of the following events EXCEPT

Options

A. The closing and opening of the heart valves during each heartbeat.
B. The movement of impulse from the SA node to all regions of the heart wall.
C. The number of time the heart beats in one minute.
D. The changes in blood volume in all chambers of the heart.

Answer

To solve the question regarding the events included in the cardiac cycle, we will analyze each option provided and determine which one does not belong to the cardiac cycle.

### Step-by-Step Solution:

1. **Understanding the Cardiac Cycle**:
The cardiac cycle refers to the sequence of events that occur during one complete heartbeat, which includes the contraction (systole) and relaxation (diastole) of the heart chambers.

2. **Evaluating Each Option**:
- **Option A**: The closing and opening of the heart valves during each heartbeat.
- This is a fundamental part of the cardiac cycle as it produces the heart sounds (LUB and DUB) and facilitates blood flow through the heart.

- **Option B**: The movement of impulses from the SA node to all regions of the heart wall.
- The SA node acts as the natural pacemaker of the heart, initiating electrical impulses that trigger heart contractions. This is also a key event in the cardiac cycle.

- **Option C**: The number of times the heart beats in one minute.
- This refers to the heart rate, which indicates how often the cardiac cycle occurs but is not an event that occurs within the cycle itself.

- **Option D**: Changes in blood volume in the chambers of the heart.
- During the cardiac cycle, as the heart contracts and relaxes, the volume of blood in the atria and ventricles changes significantly.

3. **Identifying the Exception**:
After analyzing all the options, it is clear that:
- Options A, B, and D are all events that occur during the cardiac cycle.
- Option C, which refers to the heart rate, is not an event of the cardiac cycle itself but rather a measurement of how often the cycle occurs.

### Conclusion:
The correct answer is **Option C**: The number of times the heart beats in one minute.

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