Unmyelinated and myelinated neurons in PNS can be easily differentiated as unmyelinated neurons

Options

A. Lack both Schwann cells and myelin sheath
B. Lack only myelin sheath
C. Lack only Schwann cells
D. Lack neurilemma and Nissl's granules

Answer

To differentiate between unmyelinated and myelinated neurons in the Peripheral Nervous System (PNS), we can follow these steps:

### Step 1: Understand the Structure of Neurons
Neurons are the basic units of the nervous system and can be classified into two types based on the presence or absence of a myelin sheath.

### Step 2: Identify Myelinated Neurons
Myelinated neurons have a protective covering known as the myelin sheath. This sheath is formed by specialized cells called Schwann cells in the PNS. The myelin sheath serves to insulate the axon and facilitate faster transmission of electrical signals.

### Step 3: Identify Unmyelinated Neurons
Unmyelinated neurons, on the other hand, lack this myelin sheath. Instead, they are surrounded by Schwann cells, but these cells do not form a complete myelin covering. The absence of the myelin sheath means that the conduction of nerve impulses is slower compared to myelinated neurons.

### Step 4: Recognize Key Differences
- **Myelinated Neurons**: Have a myelin sheath, which allows for faster signal transmission.
- **Unmyelinated Neurons**: Lack a myelin sheath, resulting in slower signal transmission.

### Step 5: Conclude the Differences
In summary, the primary distinguishing feature between unmyelinated and myelinated neurons in the PNS is the presence or absence of the myelin sheath. Unmyelinated neurons are characterized by the lack of this sheath, while myelinated neurons possess it.

### Final Answer
The correct option to differentiate unmyelinated neurons is that they **lack only the myelin sheath**.

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