Which of the following statement about neuron is incorrect ?

Options

A. Dendrites are afferent fibres
B. Oligodendrocytes form myelin sheath around the axons in PNS
C. Neuroglia are common source of tumours
D. Schwann cells form myelin sheath around the axons in the PNS

Answer

To determine which statement about neurons is incorrect, let's analyze each option provided:

1. **Option A**: "Dendrites are efferent fibers."
- Dendrites are indeed responsible for receiving signals and transmitting impulses toward the cell body of the neuron. However, they are not classified as efferent fibers; efferent fibers refer to axons that carry impulses away from the neuron. Thus, this statement is incorrect.

2. **Option B**: "Oligodendrocytes form myelin sheath around the axon in the PNS."
- Oligodendrocytes are glial cells that form the myelin sheath around axons in the central nervous system (CNS), not the peripheral nervous system (PNS). In the PNS, Schwann cells are responsible for forming the myelin sheath. Therefore, this statement is incorrect.

3. **Option C**: "Neuroglia are the common source of tumors."
- Neuroglia, also known as glial cells, can indeed be a source of tumors, such as gliomas. This statement is correct.

4. **Option D**: "Schwann cells form myelin sheath around the axon in the PNS."
- This statement is accurate; Schwann cells are responsible for the formation of the myelin sheath in the peripheral nervous system. Thus, this statement is correct.

After analyzing all the options, we find that the incorrect statements are **Option A** and **Option B**. However, since the question asks for one incorrect statement, **Option B** is the most clearly incorrect regarding the specific role of oligodendrocytes.

### Final Answer:
The incorrect statement about neurons is **Option B**: "Oligodendrocytes form myelin sheath around the axon in the PNS."

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