There are three different types major kinds of sleep disorder and each can be understood through sleep physiology:
1. Difficulty falling asleep.
It is caused by excessively strong or inadequately suppressed brain drives toward waking.
Best known as an insomnia.
2. Difficulty staying awake.
It is caused by excessively strong or inadequately suppressed brain drives toward sleep.
Best known as a narcolepsy.
3. Abnormal movements that occur as the depth of sleep varies over the course of the night.
For example, the movement-generating center of the brain can sometimes become active without the brain’s consciousness-generating arousal systems becoming simultaneously activated to waking levels. The classic example is sleepwalking.