What is the role of the myelin sheath in the transmission of electric impulses in the nervous system?

It is important to note that the IB syllabus expects the students to understand that "The myelination of nerve fibres allows for saltatory conduction." What this essentially means is, that the myelin sheath surrounding the axon acts as an "insulating layer" (Schacter, 2016), that allows the action potential to pass along the axon (saltatory conduction). The importance of the insulating role of the myelin sheath becomes clear when looking at people suffering from multiple sclerosis, which is a disease where the myelin sheath deteriorates. The information travelling along the axon slows down which results in several problems, one of them being that it becomes increasingly difficult to coordinate movement. The myelin sheath does not act on its own. Instead, it is broken down in smaller parts and the "little gaps" inbetween are called nodes of Ranvier. The signal travelling down the axon jumps from one node to the other speeding up the transmission of the electrical signal. As such, the myelin sheath and the nodes of Ranvier act together to allow for and to speed up the transmission of electric impulses.