The top video shows how nerve fibres conduct electricity within the nervous system; the scientific term for this is saltatory conduction; i.e. the electrical impulses jump from one gap in the myelin to the next. The conduction is very rapid.
The video below shows conduction in a demyelinated nerve that has restored conduction by a process called axonal plasticity; a big word for describing the process by which the nerve fibre recovers its ability to conduct electricity without a myelin sheath; this is called non-saltatory conduction. It is very slow.
“The conduction of electricity by nerve fibres takes energy*; clearly the amount of energy it takes to send an electrical impulse down a demyelinated nerve (bottom) is substantially more than a normal nerve (top). This has major consequence for MS’ers. Any guesses what?”
“So please imagine what the result would be if your brain had to receive electrical information from your left and right eyes at different speeds? This is something that happens to MS’ers who have had optic neuritis.”
“More on this tomorrow.”
*One of the reasons, if not the only reason, why myelin evolved was to save energy. In nature evolution tends to optimise systems that save energy; myelin is one of these. You may be interested to know that nature has evolved at least 7 different systems of myelination in different animal species. This process is called convergent evolution. Myelin must have therefore given our ancestors a major survival advantage; unfortunately, it also primed us to develop a whole host of diseases that target myelin.