If the heart rate of a person has increased but the stroke volume is same, The cardiac output will be-

Options

A. increase
B. decrease
C. remains same
D. first increase then decrease.

Answer

To determine how the cardiac output changes when the heart rate increases while the stroke volume remains constant, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definitions**:
- **Heart Rate (HR)**: The number of times the heart beats per minute.
- **Stroke Volume (SV)**: The amount of blood pumped by the heart with each beat.
- **Cardiac Output (CO)**: The total volume of blood the heart pumps per minute, calculated using the formula:
\[ \text{Cardiac Output (CO)} = \text{Stroke Volume (SV)} \times \text{Heart Rate (HR)} \]

2. **Identify the Given Information**:
- The stroke volume remains constant.
- The heart rate is increasing.

3. **Apply the Formula**:
- Since the stroke volume is constant, any increase in heart rate will directly affect the cardiac output.
- If we denote the stroke volume as \( SV \) and the initial heart rate as \( HR_1 \), the initial cardiac output can be expressed as:
\[ CO_1 = SV \times HR_1 \]
- When the heart rate increases to \( HR_2 \), the new cardiac output will be:
\[ CO_2 = SV \times HR_2 \]

4. **Analyze the Effect of Increased Heart Rate**:
- Since \( HR_2 > HR_1 \) and \( SV \) is constant, it follows that:
\[ CO_2 > CO_1 \]
- Therefore, the cardiac output will increase.

5. **Conclusion**:
- If the heart rate of a person has increased while the stroke volume remains the same, the cardiac output will also increase.

### Final Answer:
The cardiac output will increase.

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