Sympathetic nerve fibres in mammals arise from

Options

A. Sacral nerves
B. 3rd, 7th, 9th and 10th cranial nerves
C. Thoracico -lumbar segments of spinal cord
D. Cervical nerves

Answer

### Step-by-Step Solution:

1. **Understanding the Autonomic Nervous System**:
- The autonomic nervous system (ANS) is divided into two main parts: the sympathetic and parasympathetic nervous systems.
- The sympathetic nervous system is responsible for the "fight or flight" response, which prepares the body to respond to perceived threats.

2. **Identifying the Origin of Sympathetic Nerve Fibers**:
- Sympathetic nerve fibers are primarily involved in activating the body's response to stress or danger.
- They originate from specific regions of the spinal cord.

3. **Locating the Spinal Cord Segments**:
- The sympathetic fibers arise from the thoracic and lumbar regions of the spinal cord.
- Specifically, they originate from the thoracolumbar segments, which include the first thoracic vertebra (T1) to the third lumbar vertebra (L3).

4. **Evaluating the Options**:
- The options provided are:
- A) Sacral nerves
- B) 3rd, 7th, 9th, 10th cranial nerves
- C) Thoracicolumbar segments of the spinal cord
- D) Cervical nerves
- The sacral nerves and cranial nerves listed do not correspond to the sympathetic nervous system's origin.

5. **Conclusion**:
- The correct answer is **C) Thoracicolumbar segments of the spinal cord** as this is where the sympathetic nerve fibers arise.