Five Stages Of Sleep
Electrical activity in the brain recorded during sleep
1. Light sleep: Muscles relax, body temperature drops, you drift in and out of wakefulness. Fragmented images may appear.
2. Transition: Heart rate, breathing and waves of electrical activity in the brain slow down
3. Deep Sleep: Large, slow waves in the brain.
4. The body becomes harder to awaken as it closes itself off to stimuli. In the fourth stage the waves are similar, but slower.