After around five minutes, sleep progresses to NREM stage two, where the body temperature and heart rate drop, and you sleep more deeply. (1) Now, the brain initiates two unique forms of activity: sleep spindles, which help with memory and learning and block out external stimuli to keep you asleep, and K-complexes, which help block reactions to harmless light or sounds and wake you up if something is perceived as dangerous. Stage two of NREM accounts for about half the time we are asleep.
NREM stage three is known as ”slow-wave sleep” or deep sleep. This stage is integral to repairing and restoring the body, building bone and muscle, and strengthening the immune system. This leads to waking up feeling refreshed in the morning. As people get older, however, they tend to spend less time in slow-wave sleep and more time in NREM stage two. (1)
What Is REM Sleep?
Rapid eye movement (REM) sleep is an active sleep stage most closely associated with dreaming. During this time, the arm and leg muscles become temporarily disabled, preventing the body from acting out when dreaming. (2) The eyes and diaphragmatic breathing muscles remain active, and breathing becomes more erratic and irregular. The first REM cycle usually begins around 90 minutes after we fall asleep and occurs after NREM sleep stages one to three. The first period of REM sleep at the start of the night lasts for around 10 minutes and then gradually increases, with the last cycle lasting up to one hour. (1)
It might not feel like it on Monday morning, but we spend around one-third of our life asleep as humans. The homeostatic need for sleep – our sleep drive – and a wake-promoting process that heightens during the day to keep us energized and alert regulates the sleep-wake cycle. As day returns to night, the wake-promoting process eases, allowing the sleep drive to take over and enhance the possibility of a deep, restful slumber. When adequate rest is achieved, the wake-promoting process fires up, and the cycle begins again. (3)
Speaking of our normal sleep-wake cycle, our breakthrough BioSeries™ technology in our Sleep BioSeries™ Melatonin moves to the beat of our normal sleep rhythm. The melatonin is released in phases to support falling asleep and staying asleep to wake up rested.*