Neural signal through the sympathetic nerve (part of ANS) increases cardiac output because of -

Options

A. Increasing the rate of heart beat
B. Increasing the strength of ventricular contraction
C. Both a and b
D. Increasing the stimulation of vagus nerve

Answer

To answer the question regarding how neural signals through the sympathetic nerve (part of the autonomic nervous system) increase cardiac output, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding the Autonomic Nervous System (ANS)**:
- The ANS is divided into two main parts: the sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS).
- The SNS is responsible for the 'fight or flight' response, which prepares the body for stressful situations.

2. **Role of the Sympathetic Nervous System**:
- The SNS increases the heart rate (the number of beats per minute).
- It also enhances the strength of each heart contraction (contractility).

3. **Cardiac Output Definition**:
- Cardiac output (CO) is defined as the volume of blood the heart pumps per minute.
- It can be calculated using the formula:
\[ \text{Cardiac Output} = \text{Stroke Volume} \times \text{Heart Rate} \]
- Where stroke volume (SV) is the amount of blood pumped by each ventricle per heartbeat.

4. **Effects of Sympathetic Activation**:
- When the sympathetic nervous system is activated, both the heart rate and stroke volume increase.
- An increased heart rate means more beats per minute.
- An increased stroke volume means that each beat pumps more blood.

5. **Conclusion**:
- Since both heart rate and stroke volume are increasing due to sympathetic stimulation, the overall cardiac output will also increase.
- Therefore, neural signals through the sympathetic nerve increase cardiac output by increasing both the heart rate and the strength of heart contractions.

### Final Answer:
Neural signals through the sympathetic nerve increase cardiac output because they increase both the heart rate and the strength of heart contractions, leading to a higher stroke volume and thus a higher cardiac output.

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