What is the myelin sheath primarily composed of?

The myelin sheath is primarily composed of lipids, which serve several important functions in the nervous system. This fatty substance wraps around the axons of neurons, forming an insulating layer that facilitates the rapid conduction of electrical impulses along the nerve fibers. The presence of myelin increases the speed of signal transmission by allowing impulses to jump between the nodes of Ranvier, which are small gaps in the myelin sheath. Additionally, the lipid composition helps maintain the structural integrity of the sheath and provides protection to the underlying nerve fibers.

While proteins play a role in the structure and function of myelin, particularly in forming myelin-related proteins, they do not make up the primary component. Carbohydrates and DNA are not significant components of the myelin sheath; carbohydrates are found in various cellular structures and processes, while DNA is primarily associated with genetic information within the nucleus of cells. Thus, the correct answer reflects the essential role of lipids in the formation and function of the myelin sheath.