Sympathetic nerve fibres in mammals arise from

Options

A. Sacral nerve
B. Cervical nerves
C. Thoracolumbar nerves
D. III, IV, X cranial nerves

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks where sympathetic nerve fibers in mammals originate. This requires knowledge of the anatomy of the nervous system, specifically the sympathetic nervous system.

2. **Identifying Sympathetic Nerve Fibers**: Sympathetic nerve fibers are part of the autonomic nervous system, which controls involuntary bodily functions. They are primarily responsible for the "fight or flight" response.

3. **Locating the Origin of Sympathetic Fibers**: Sympathetic fibers arise from specific regions of the spinal cord. These fibers are known to originate from the thoracic and lumbar regions.

4. **Analyzing the Options**:
- **Option A: Sacral nerve** - This is not correct as sacral nerves are part of the parasympathetic nervous system.
- **Option B: Cervical nerves** - This is also incorrect; cervical nerves do not primarily give rise to sympathetic fibers.
- **Option C: Thoracolumbar nerves** - This is correct as it refers to the thoracic and lumbar regions of the spinal cord where sympathetic fibers originate.
- **Option D: 3rd, 4th and 10th cranial nerves** - These are associated with the parasympathetic nervous system, not the sympathetic.

5. **Conclusion**: Based on the analysis, the sympathetic nerve fibers in mammals arise from the thoracolumbar region of the spinal cord, confirming that the correct answer is **Option C**.

**Final Answer**: Sympathetic nerve fibers in mammals arise from **thoracolumbar nerves** (Option C).

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