Narcolepsy is a concept where a person or animal is suddenly overcome by sleepiness and falls asleep. During this disorder, sleep lasts from only seconds to sometimes hours. Unfortunately, for those with the disorder it leads them to have cataplexy, complete loss of muscle tone. Cataplexy usually occurs during REM sleep in people who don't have narcolepsy, but when cataplexy occurs in people who have narcolepsy they can fall and be completely awake even though they can't move. Also, people with narcolepsy fall into REM sleep immediately causing them to not be able to wake up. Hallucinations occur during a narcoleptic's REM sleep as well. The disorder of narcolepsy makes me wonder how its treatment of medication, modafinil, works. Also, are there any biological functions that are affected that cause a person to be a narcoleptic?