Answer:
1. Covering- Myelin sheath
2. Surrounding cell- oligodendrocytes
Explanation:
Oligodendrocytes are one of the type of Glial cells which perform many additional functions other than conduction.
The plasma membrane of the oligodendrocytes surrounds the axon and wrap them in a spiral manner in a way that it forms the layer. This provides protection, support and insulates them and the layer is known as the myelin sheath.
In the given question, since the observer has observed that the cell which surrounds the neuron is present in the brain and also a sheath, therefore, the glial cell which forms the sheath will surround the cell that is known as oligodendrocytes. The Schwann cells like oligodendrocytes form the myelin sheath in the peripheral nervous tissue.
oligodendrocytes provide the myelin coverings to axons within the CNS. The oligodendrocytes have arm like processes that extend out to as many as 60 nerve fibers and create multiple spiral layers of compressed cell membrane that form section of the myelin covering the axons.
