It acts an insulator on the neurons. The neurons are covered with it and hence the nerve impulses have to jump over the myelin sheath to reach other neurons. This causes nerve impulses to move rapidly from neuron to neuron.
There are 1000 meters in 1 kilometer, and so you cover 10,000 meters in a 10k race
hope this helps
first blank: farsightedness (hyperopia)
second blank: nearsightedness (myopia)
