While reading chapter 5, I came across a sleeping disorder which particularly struck me. It is referred to as, Narcolepsy. People who have this disorder experience an overwhelming urge to sleep at any given point during their day. Due to this urge, they participate in unexpected and rapid sleep episodes. These episodes can range anywhere from a few seconds to an hour.
Anything and everything can trigger these urges. It has been noted that people with this disorder have fell asleep while in the shower, driving, watching their favorite movies, working, laughing, having sex, etc etc. During the moment of these urges, people with narcolepsy are involved with cataplexy, meaning all their muscles become completely limp. Cataplexy occurs when everyone sleeps, but with narcolepsy people, they are fully alert but just can't move. In addition, normal sleepers do not fall into REM sleep ("stage of sleep during which the brain is most active and during which vivid dreaming most often occurs") till about an hour after dozing off, where as a narcolepsy person falls directly into REM sleep. This often times causes the person to have vivid hypnagogic hallucinations.
In addition to the hormone orexin contributing highly to this disorder, narcolepsy often times occurs after brain damage is done in an accident. Today there is not a specific medication out that will cure these sudden sleep urges, but narcolepsy patients are often times proscribed a medication called modafinil, which pushes wakefulness throughout their day.
An example of a man with narcolepsy, he falls asleep during the duration of a work meeting.