Myelin

Emerging 425 million years ago during our evolution, the substance known now as myelin enables the split-second acceleration of nerve impulses. Remarkably, myelin occupies nearly half the volume of the human brain and is critical for our intellectual and motor performance. We owe our reflexes to myelin: it is what makes us brake when a child dashes out onto the road, or snatch away a hand absent-mindedly placed on a burning hot stove.The study of myelin's role in the conduction of nerve impulses has led to a better understanding of several diseases including multiple sclerosis, Guillain-Barre syndrome, Charcot-Marie-Tooth peripheral neuropathies, and other genetic diseases of myelin.