What Happens During Sleep
Many people think of their sleeping bodies as if they were cars parked for the night–motionless, engines off, headlights dimmed. But sleep is an amazingly complex state of being. As we sleep, muscles tense and relax. Pulse, temperature and blood pressure rise and fall. Chemicals crucial for well-being course through the blood stream. The brain, like a Hollywood director, conjures up fantastic stories, complete with a plot, characters and action.
You don’t simply “fall” asleep. You descend slowly through different levels. As you close your eyes and drift off, you enter the first stage of what is called quiet sleep. Your brain produces irregular, rapid waves, and muscle tension decreases. You breathe smoothly, and mundane thoughts float through your mind. If roused, you might jerk awake quickly and deny that you’d slept at all.
In stage 2 of quiet sleep, your brain waves become larger, punctuated by occasional sudden bursts of electrical activity. You’ve definitely crossed the border between wakefulness and sleep. If someone lifted your eyelids gently, you wouldn’t waken; your eyes no longer respond to stimuli.
As you descend into stage 3, your brain waves become slower and bigger. In this state of deep slumber, your bodily functions slow down even more. Finally stepping into stage 4, you reach deepest sleep, the most profound state of unconsciousness. On an EEG (electroencephalogram), your brain waves would appear extremely large and slow. You are so “dead to the world” that a thunderstorm might not wake you.
This step-by-step journey into oblivion usually takes more than an hour. Then you begin to climb upward, moving rapidly through the same sleep stages as before, not all the way to full wakefulness but in active sleep. Because the pupils dart back and forth, this stage is called Rapid Eye Movement or REM sleep. (The four stages of quiet sleep are often referred to as non-REM or NREM sleep.)
During REM, your brain waves resemble those of waking rather than of quiet sleep. The large muscles of your torso, arms and legs are paralysed, although your fingers and toes may twitch. You breathe quickly and slowly, the flow of blood through your brain accelerates. REM sleep is the time of vivid dreaming, and if wakened, you’d probably recall a fragment of a fantasy.
After about ten minutes in REM sleep, you descend the sleep staircase again. The entire cycle of REM and NREM stages takes roughly 90 minutes. Early in the night, the periods spent in the deepest stages of quiet sleep are longer. In the second half of the night, REM sleep predominates. By morning, you go around the sleep circuit four or five times.
This pattern changes gradually throughout life. From infancy to adulthood, REM periods dwindle to less than a quarter of a night’s sleep.
By their thirties, men spend less time in the very deep stages of REM sleep. Women begin to sleep less deeply in their fifties. By age 65, both sexes spend half as much time in deep sleep as they did when 25.
The lighter sleep stages increase later in life, and REM shrinks to about a fifth of total sleep time.
If you snore and sleep with a partner you will probably disturb them who will probably waken you to tell you. It is important therefore that you find a cure for snoring. Should you not both of you could suffer from sleep deprivation.
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