Figure 44.3 Glial Cells Insulate Axons (A) Schwann cells produce layers of myelin, a type of cell membrane that provides electrical insulation to the axon. At the intervals between Schwann cells—the nodes of Ranvier—the axon is exposed. Action potentials travel along the axon by “jumping” from node to node, as described in Key Concept 44.2. (B) A myelinated axon, seen in cross section through an electron microscope.