The Sleep Cycle

Although made up of five different cycles, sleep is typically characterized by two states-REM and non-REM. Non-REM sleep has four stage, ranging from drowsiness to deep sleep; REM sleep is where dreams occur, breathing and heart rate increase and become irregular, the muscles relax and the eyes move back and forth, which is why it is often referred to as "rapid eye movement."

STAGE 1 (Non-REM): The transition phase between waking and sleeping. Eye movements slow, and you have trouble staying awake.

STAGE 2 (Non-REM): Where real sleep begins and bodily functions slow down. you call deeper and deeper into sleep, although you still can be easily awakened by sounds.

STAGE 3 (Non-REM): The transition phase into deep sleep. The heart rate slows down and muscles relax completely.

STAGE 4 (Non-REM): Where breathing and heart rate are at their slowest. If you awaken during this phase, you will probably be groggy or disoriented.

STAGE 5 (REM): rapid eye movements characterize the phase, known as "THE DREAM STAGE." If you wake, you may be able to explain a dream you were having.