Final answer:
Oligodendrocytes are the type of glial cell that form the myelin sheath in the central nervous system, which is essential for insulating axons and increasing neural transmission speed.
Step-by-step explanation:
The type of glial cell that makes up myelin in the central nervous system (CNS) is the oligodendrocyte. These cells have processes that reach out to and wrap around multiple axon segments, forming the myelin sheath, which serves as insulation and increases the speed at which electrical impulses travel along nerve cells.
In contrast, the Schwann cells perform a similar myelination function in the peripheral nervous system (PNS), but a single Schwann cell wraps around only one axon segment. The other glial cells mentioned serve different functions within the CNS: astrocytes regulate the chemical environment and help maintain the blood-brain barrier, microglia act as phagocytes in immune surveillance, and ependymal cells produce cerebrospinal fluid.
The correct option for the type of glial cell that makes up myelin in the CNS: 2) Oligodendrocytes. This answer is based on the provided information from the study materials.