Myelinated refers to nerve fibers that are covered with a protective sheath called myelin. This sheath is made of fatty substances and helps to insulate the nerve fibers, allowing electrical signals to travel more quickly and efficiently along the nerves. Myelination is crucial for the proper functioning of the nervous system. In the human body, myelinated fibers are found in both the central nervous system (CNS) and the peripheral nervous system (PNS). The presence of myelin increases the speed of signal transmission, which is essential for rapid communication between different parts of the body, such as in reflex actions and coordinated movements.