Myelin 101: What It Is and Why It Matters

Duct tape on a soaker hose. Wiring insulation or tape on electrical wires. A toll road with limited exits. Take your pick on metaphors for myelination. Each metaphor is trying to communicate that myelin makes signalling faster. Much faster.

We need quick communication between different regions of our brains and between our brains and the rest of our bodies to do “basic” things. Crawling, remembering where you put your coffee cup, smelling and registering your favorite blossom all require myelination. So what is it? Myelin is a layer of mostly fat and some proteins that is wrapped around neurons by other, specialized cells called oligodendrocytes. As the layers of myelin, the myelin sheath, are built up along the neuron, messages can be relayed more quickly.

Building up the myelin sheaths is a gradual process that begins in the third trimester of pregnancy and continues all the way into young adulthood. In individuals with Down syndrome, this process is often delayed by as much as 12 months. Knowing that myelination is delayed and that even the “simple” task of crawling requires quick communication within the brain and to the body, one can quickly appreciate that people with Down syndrome face extra challenges right from the start from a neurobiological perspective. My takeaway: people with Down syndrome conquer so much with each and every developmental milestone and their determination should rightfully be celebrated.

Neuron_with_oligodendrocyte_and_myelin_sheath.svg: *Complete_neuron_cell_diagram_en.svg: LadyofHats derivative work: Andrew c, Public domain, via Wikimedia Commons