Question

What type of cell makes up the myelin sheath of a motor neuron?

Answer 1

Myelinated Schwann cells wrap around axons of motor and sensory neurons to form the myelin sheath.

Explanation:

Individual myelinating Schwann cells cover about 100 micrometers of an axon.

Myelinating Schwann cells begin to form the myelin sheath in mammals during foetal development and work by spiralling around the axon. A well developed Schwann cell is like a rolled up sheet of paper, with layers of myelin in between each coil. The inner layers of wrapping are predominantly membrane material and form the myelin sheath. While the outer most layer of nucleated cytoplasm forms the neurolemma.

The myelin sheath is not continuous. The gaps between adjacent Schwann cells are called as the nodes of Ranvier.

Each myelinating Schwann cell provides insulation to only one axon. It greatly increases speed of conduction and saves energy.
Schwann cells also play an important role in supporting nerve cell regeneration.