Non Myelinated axons differ from myelinated that they

Options

A. Are more excitable
B. Lack nodes of Ranvier
C. Are not capable of regeneration
D. Are not associated with Schwann cells

Answer

To understand how non-myelinated axons differ from myelinated axons, we can analyze the characteristics of both types of axons step by step.

### Step-by-Step Solution:

1. **Definition of Myelinated and Non-Myelinated Axons**:
- Myelinated axons are covered with a myelin sheath, which is a fatty layer that insulates the axon and facilitates faster transmission of electrical impulses.
- Non-myelinated axons lack this myelin sheath and are generally slower in conducting nerve impulses.

2. **Excitability**:
- Myelinated axons are more excitable due to the presence of the myelin sheath, which allows for saltatory conduction. This means that the nerve impulse jumps from one node of Ranvier to another, speeding up the transmission.
- Non-myelinated axons do not have this feature, making them less excitable compared to myelinated axons.

3. **Presence of Nodes of Ranvier**:
- Myelinated axons have nodes of Ranvier, which are gaps in the myelin sheath that facilitate rapid conduction of impulses.
- Non-myelinated axons lack these nodes, which means they do not have the ability for saltatory conduction. Instead, the impulse travels continuously along the axon, resulting in slower conduction.

4. **Regeneration Capability**:
- Both myelinated and non-myelinated axons have the potential for regeneration after injury, so the statement that non-myelinated axons are not capable of regeneration is incorrect.

5. **Association with Schwann Cells**:
- Myelinated axons are associated with Schwann cells that form the myelin sheath.
- Non-myelinated axons can also be associated with Schwann cells, but they do not have the myelin sheath.

### Conclusion:
The primary difference between non-myelinated and myelinated axons is that non-myelinated axons lack nodes of Ranvier, which leads to slower conduction of nerve impulses compared to the faster conduction seen in myelinated axons.