The function of the myelin sheath in nerve cells is to insulate axons and enhance the speed of electrical signal transmission. This protective layer, composed of lipid-rich material, allows for faster propagation of action potentials through a process called saltatory conduction. Myelin sheath gaps, known as nodes of Ranvier, facilitate rapid signal jumps between nodes, increasing the efficiency of communication within the nervous system. Proper myelination is crucial for effective neural function and coordination.