Question

Which of the following has non myelinated nerve fiber?

• A. Optic nerves
• B. Cranial nerves
• C. Spinal nerves
• D. Autonomic nerves

Answer 1

The correct option is D

Autonomic nerves

The correct option is option D.

Explanation of correct option:

1. An insulating layer, or sheath, which forms around the nerves, comprising those in the spinal cord and the brain is the myelin sheath.
2. The myelinated nerve fibers are the nerve fibers, which are covered by a myelin sheath.
3. These nerve fibers conduct fast and saltatory conduction of nerve impulses.
4. The autonomic nerves are the component of the peripheral nervous system, which monitors involuntary physiologic procedures like blood pressure, heart rate, digestion, etc.
5. These are the motor neurons situated in the neck, head, pelvis, abdomen, and thorax.
6. The autonomic nerves are the non-myelinated fibers, that is, they are devoid of the myelin sheath, and conduct slow but smooth conduction of nerve impulses.

Explanation of incorrect options:

Option A:

1. Optic nerves are a group of more than one million nerve fibers, which conduct visual messages.
2. These are the cranial nerves, which transmit electrical impulses from the eyes to the brain.
3. The optic nerves are myelinated nerve fibers.

Option B:

1. A set of twelve paired nerves situated in the back of the brain are the cranial nerves.
2. These nerves transmit electrical signals between the brain, neck, torso, and face.
3. These nerves are myelinated, that is, they are covered by a myelin sheath.

Option C:

1. The group of nerve fibers associated with the spinal cord, which conduct information to and away from the spinal cord is the spinal nerves.
2. These nerves innervate all the regions of the body apart from the neck and head region.
3. These nerves are also myelinated, that is, enveloped by a myelin sheath.

Final answer: Autonomic nerves has non-myelinated nerve fiber.