Sleep Mechanics

Do We Need Sleep?

          One of the most common questions about sleeping is that, "Do we actually need sleep?"  The answer is yes, although our bodies can be trained to do with gradually less sleep.  There may be some people who claim that they need no sleep at all, but you will find that they tend to take occasional five to ten-minute naps during the day.  We need sleep for our body to relieve stress, to grow, and also to balance our bodily chemicals.

          Around the beginning of the century it was thought that chemicals such as lactic acid, carbon dioxide, and cholesterol were collected in our brain while we were awake and were depleted during sleep.  But about sixty years later we began experimenting on how long a human body could go without sleeping.  Randy Gardner, a 17-year-old high-school student from San Diego, stayed awake for eleven complete days.  Although he felt nauseous at times, had difficulty reading, and suffered temporary memory lapses, he had no long term emotional or physical side-affects of the experiment.  Measurements have been taken, however, to prove that there are some chemical changes during sleep deprivation that concludes the fact that our body needs sleep.

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Why We Sleep

          So now that we know why we need sleep, we need to know what is the thing that actually puts us to sleep.  Some may recognize the name melatonin, because it is sometimes prescribed for jet-lag or sleep deprivation.  But we also create this chemical inside our bodies, although it is in much smaller portions.  Melatonin is a hormone secreted from the pineal gland in the center of our brain.  It is released when our eyes begin to register that the sun is beginning to set and darkness begins to fall.  This is what makes you go to sleep and is also used in our body to regulate our sleep-wake cycles.  If you wonder why older people tend to sleep less then younger people, it is because the amount of melatonin produced in our body seems to lessen as we age.

          The term of "rapid eye movements" was coined in 1952 by Fredrick Van Eeden.  Van Eeden discovered this while doing a study on sleep noticed the eyes of his subjects moving beneath their closed eyelids.  He watched as they moved back and forth, as if they were watching an intense tennis match.  From then on sleep was characterized into two areas, REM sleep and NREM sleep, properly coined by non-rapid eye movement.  These two areas are quite different from each other in that people awakened from REM sleep could usually remember vivid dreams whereas only six percent of people awakened during NREM claimed to have been dreaming.  In fact, people in the REM state show more brain activity than those in a wakeful state.  But those in NREM sleep show more characteristics toward the unconscious brain.

          REM sleep seems more psychologically important and less physically important.  If someone has a night deprived of REM sleep they tend to become overly sensitive, have bad memory recall, and unable to concentrate.  While people lacking NREM sleep are clumsy, sluggish, and look to be very tired.  Whereas people deprived of NREM sleep only suffer a temporary inconvenience, people who have lost REM sleep have more trouble coping with stress over a long period of time and are irritated very easily.

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Stages of Sleep

          A typical night's sleep consists of a number of cycles lasting about 90 minutes in length.  Each of these cycles is made up of four separate stages.

The Hypnagogic Phase - This stage is the transitory stage between closing our eyes and sleeping.  This is a brief period where we have visions that aren't dreams but would rather resemble still images.  These images often go unnoticed or are forgotten.

Stage 1 - During this period we are just falling asleep.  Our heart rate begins to slow and our muscles relax.  The EEG is irregular and lacks consistency of alpha waves that occur when we are awake and relaxed.

The Myoclonic Jerk - It is not abnormal for a person during stages one and two of sleeping does a short convulsion of the body occur.  Researches are quite undecided on this subject.  Common views are that this occurrence marks a transition between these two stages and that your brain, noticing your heart and breathing rate decreasing more rapidly than normal, sends out a burst of electrical activity to your muscles.

Stage 2 - A deeper sleep than stage one. The EEG would show bursts of activity called "spindles", and an occasional sharp rise and fall in amplitude.

Stage 3 - Sleep becomes deeper and spindles disappear from the EEG.  The spindles are replaced by long delta waves.  The sleeper is more difficult to wake during this stage, but can be aroused by calling out a familiar name.  Often times a loud sound, such as a door slamming, will be ignored.

Stage 4 - At this stage the sleeper enters "delta sleep" and will spend nearly 30 minutes in this stage.

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Dreams In Series

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The Sleep Cycle

          Once you complete the four stages of sleep (which takes about an hour) you begin to cycle back into stage one sleep, but instead of falling back into stage four you reach another stage of sleep called REM sleep.  An EEG would record brain waves resembling those you would see when you are active.  The following diagram shows our sleep cycle:

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