Stage V. Stage V is remarkably different from the previous stages. The brain and body become active, increasing heart rate and blood pressure. The eyes shudder quickly back and forth, giving this stage the name Rapid Eye Movement (REM) sleep. EEG patterns for REM sleep are much like those during wakefulness and include many fast beta-rhythms. It may even be that the brain works harder during REM sleep than when awake. REM sleep usually lasts anywhere from 11 to 25 minutes, typically longer in the later sleep cycles of the night. Approximately 25% of all sleep is REM sleep in adults, in children it is even higher. On completion of a phase of REM sleep, the brain and body return to Stage I, and begin another sleep cycle.
The differences between NREM and REM sleep tell a story. NREM sleep deals mainly with repairing and relaxing the body, while REM sleep has deals with the innerworkings of the brain. Even though they But they may certainly be interconnected. Researchers have speculated that NREM sleep also functions to recharge the brain by allowing depleted glycogen supplies to be replenished. Further hypotheses state that the high levels of neurological activity during REM sleep allows ions to be pumped across the membranes of neurons in the brain and stimulate another cycle of NREM sleep.
NREM Sleep Stage V