Question

Myelin sheath of nerve fiber is produced by
A. Axon.
B. Connective tissue.
C. Schwann cells.
D. Neuroglia.

Answer 1

Hint: Nerve fibres or neurons have a long extension named axon. The axon is covered by a membrane in some neurons while this membrane is absent in some neurons. It is nothing but the myelin sheath. The axons having myelin sheath are known as myelinated neurons.

Complete answer:
Axons of nerve cells conduct impulses away from the cell body.
Its cytoplasm is called axoplasm and plasma membrane as axolemma.
The axon is covered uniformly by a neurilemma. The axon is covered first covered by myelin or medullary sheath and then by a neurilemma
The myelin sheath is a layer that permits impulses to transmit fastly and effectively along with the nerve cells.
The Schwann cells cover the myelin sheath in the peripheral nervous system.
Also,
Neuroglia: These are non-excitable cells found in the central nervous system around the neurons to support and protect them. These are- oligodendrocytes, astrocytes, microglia.
Connective tissue: It is the type of tissue found in animals whose main function is binding other tissue systems or organs.

The correct answer for the above question is option( C ).

Note: Nerve fiber- Axon or nerve fiber is a single long thread with neurofibrils but without Nissl granule and emerges from a special protuberance on the cell body called the axon hillock.
The following parts are also found in the main body of a nerve cell :
Nissl granules: It is a large specialized basophilic body found in neurons, and it is rich in iron and concerned with protein synthesis.
Neurilemma: It is the outer membranous covering of a nerve fiber.