Your sleep is unique, like fingerprints.
The quality and length of sleep is different for every individual. Some wake up refreshed and ready for the day after getting only as little as five hours of sleep. Others need to get up to 10 hours worth of shuteye. On average, though, adults need 7 to 8 hours of sleep.
As we all know, sleep is as much an essential component of life among other animal species as it is with us—the only variables apparently being the duration and depth of sleep. The natural triggers for sleep have been biologically synchronized with the time of day. For most animals, including us humans, the darkness of night triggers sleep.
Sleep is the time when the body can recharge and repair itself without being burdened by the daytime rigors and pressures of survival, or be distracted by our conscious brain’s worries. Think of it like a roadworks project: The construction gets done faster and more thoroughly when there’s no traffic to bother the workmen and there’s no sun to weaken them and slow down the work.
So when you wake up the next day after a good night’s sleep, it’s just like your body and brain is riding on newly paved and widened road—the body ache is gone, any wound you have has healed faster, you’ve remembered the lyrics to a song, the name of a friend you bumped into yesterday (but was too tired to remember his name at the time), and ideas for an office presentation are coming in torrents. That’s the miracle of sleep, something akin to being born again every morning.
Sleep is a heightened anabolic state, accentuating the growth and rejuvenation of the immune, nervous, skeletal and muscular systems
Sleep timing is controlled by the circadian clock, sleep-wake homeostasis, and in humans, within certain bounds, willed behavior. The circadian clock—an inner timekeeping, temperature-fluctuating, enzyme-controlling device—works in tandem with adenosine, a neurotransmitter that inhibits many of the bodily processes associated with wakefulness. Adenosine is created over the course of the day; and high levels of this neurotransmitter lead to sleepiness. In diurnal animals, sleepiness occurs as the circadian element causes melatonin production and a gradual decrease in core body temperature. The timing is affected by one’s chronotype. It is the circadian rhythm that determines the ideal timing of a correctly structured and restorative sleep episode.
Normal sleep consists of two main states, designated rapid-eye movement (REM) and non-rapid- eye-movement (non-REM) sleep. It is REM sleep that is most often associated with dreaming. The stages of sleep are further broken down into the following:
Light sleep stage 1. We drift in and out and can be awakened easily. Our eyes move slowly and muscle activity slows.
Light sleep stage 2: Our eye movement stops and our brain waves become slower, with occasional bursts of rapid waves called sleep spindles.
Deep sleep stage 3: Extremely slow brain waves called delta waves appear, interspersed with smaller, faster waves.
Deep sleep stage 4: The brain produces mostly delta waves. There are no eye movements and no muscle activity.
Stage 5: REM sleep. Breathing becomes more rapid, irregular and shallow. The eyes jerk rapidly while limb muscles become temporarily paralyzed. Dreams almost always happen in this stage, but may occur in other sleep stages.
It takes about 2 hours to go through all five stages of sleep, after which they are normally repeated. REM sleep usually occurs about 90 minutes after we fall asleep. Adults spend half their sleep time in stage 2 sleep, 20 percent in REM sleep, and 30 percent in the other stages. Infants, on the other hand, start out spending half their sleep time in REM sleep. Older people spend less time in delta sleep (stages 3 and 4), and some may not experience it at all.
So, yes, indeed, all humans need sleep, but every individual has unique requirements to be able to classify him or herself to have had sound sleep. So how would you know if you have been sleeping well or sleeping soundly the past days, or nights? Here’s a handy rule of thumb: If you’ve found yourself suddenly dozing off at the dinner table, or while watching an engaging movie, or maybe even during a conversation or (heaven forbid) while driving, that’s a sure sign that’s something’s amiss with your own body clock.
Don’t ignore these warning signs, because if your sleep problems become chronic, more serious physical and mental issues will almost certainly arise.