The total duration of the cardiac cycle is 0.8 seconds. If a person is suffering from fever and their heartbeat rate increases, then the duration of their cardiac cycle will

Options

A. remain the same
B. increase
C. decrease
D. become irregular

Answer

To solve the question regarding the effect of an increased heartbeat rate on the duration of the cardiac cycle, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Cardiac Cycle**: The cardiac cycle refers to the sequence of events in one complete heartbeat, which includes the contraction and relaxation of the heart chambers. The total duration of the cardiac cycle is typically around 0.8 seconds at a normal resting heart rate.

2. **Identify the Relationship Between Heart Rate and Cardiac Cycle Duration**: There is an inverse relationship between heart rate and the duration of the cardiac cycle. This means that as the heart rate increases, the duration of the cardiac cycle decreases. Conversely, a lower heart rate corresponds to a longer duration of the cardiac cycle.

3. **Consider the Effect of Fever on Heart Rate**: When a person has a fever, their body temperature rises, which often leads to an increase in heart rate (tachycardia). This is a physiological response to help meet the increased metabolic demands of the body during fever.

4. **Apply the Relationship to the Given Scenario**: Since the question states that the heartbeat rate increases due to fever, we can conclude that the duration of the cardiac cycle will decrease. This is because the heart is beating faster, thus completing each cycle in a shorter amount of time.

5. **Choose the Correct Answer**: Based on the analysis, the correct answer is that the duration of the cardiac cycle will decrease.

### Final Answer:
The duration of the cardiac cycle will decrease.

---