Which one of the following pairs of structures distinguishes a nerve cell from other types of cells?

Options

A. Vacoules and fibres
B. Flagellum and medullary sheath
C. Nucleus and mitochondria
D. Cell body of a neuron and dendrites

Answer

To solve the question "Which one of the following pairs of structures distinguishes a nerve cell from other types of cells?", we will analyze the options provided and identify the unique structures that are characteristic of nerve cells (neurons).

### Step-by-Step Solution:

1. **Understanding the Structure of a Nerve Cell**:
- A nerve cell, or neuron, has a unique structure that includes a cell body, dendrites, and an axon. The cell body contains the nucleus, while dendrites are extensions that receive signals, and the axon transmits signals away from the cell body.

2. **Analyzing the Options**:
- **Option 1: Vacuoles and Fibers**:
- Vacuoles are primarily involved in storage and are not specific to nerve cells. Fibers are more related to plant cells for support. Thus, this option does not distinguish nerve cells.

- **Option 2: Flagellum and Medullary Sheath**:
- Flagella are structures for movement found in some cells (like sperm cells) but are not present in neurons. The medullary sheath (myelin sheath) is present in neurons, but the pairing with flagellum makes this option incorrect.

- **Option 3: Nucleus and Mitochondria**:
- While both structures are present in nerve cells, they are not unique to neurons. Nucleus is found in all eukaryotic cells, and mitochondria are present in nearly all cell types for energy production. Thus, this option does not distinguish nerve cells.

- **Option 4: Cell Body of a Neuron and Dendrites**:
- The cell body is essential for the functioning of a neuron, housing the nucleus and organelles. Dendrites are unique extensions that receive signals from other neurons. This pairing is specific to nerve cells and distinguishes them from other cell types.

3. **Conclusion**:
- The correct answer is **Option 4: Cell Body of a Neuron and Dendrites**. This pair of structures is distinctive to nerve cells and plays a crucial role in their function.