31. When a peripheral fiber is severed, the myelin sheath provides a track along which regrowth can occur. 32. The thickness of the myelin sheath on motor neurons determines how quickly electrical impulses travel along them. 33. There is still a myelin sheath present-just in far lower amounts compared to the white ramus communicans. 34. Each arm reaches out to a nerve fiber and spirals around it, creating a myelin sheath . 35. A myelin sheath is a lipid protective coating that covers and protects nerve cells ( axons ). 36. Schwann cells are the cells in the peripheral nervous system that create and maintain myelin sheaths on neurons. 37. In 1838, Theodor Schwann began studying white and grey matter in the brain, and discovered the myelin sheath . 38. Researchers in New York have successfully cured leukodystrophy in mice, using skin cells to repair damaged myelin sheaths . 39. The disease involves an enzyme deficiency that causes the myelin sheath surrounding nerves to the brain to degenerate. 40. The myelin sheath of long nerves was discovered and named by German histologists of the late 19th century.
