Thursday, March 12, 2009

Sleeping Disorders - The Phases of Sleep

Half a century ago scientists discovered what our bodies and brains were doing when we experienced our deepest and most memorable dreams. Eugene Aserinsky and Nathaniel Kleitman with assistance from William C. Dement at the University of Chicago discovered REM sleep in 1953,

While we are asleep our brains and bodies experience two distinct phases. The most widely known is REM or rapid eye movement sleep. This is the less common one; the more regular phase is known as non-REM sleep.

Relaxation is indicated by alpha waves seen on an EEG of the brain. With our mind free of thoughts and eyes closed it is the first stage we undergo before falling asleep. Delta waves replace the alpha waves as drowsiness commences. When the mind reaches this stage itindicates we have fallen asleep and entered the slow wave or non-REM stage of sleep.

Slow wave sleep is associated with muscle rehabilitation and growth through the release of anabolic hormones and cytokines. The cells of the body are repaired and immune defenses maintained. It helps us recover from the active rigors of the day. Pregnant women and fast growing children and adolescents experience longer periods of slow-wave sleep than those off us who no are not experiencing periods of growth.

Non-REM sleep can be divided into three phases.

Stage 1 is the beginning of sleep. If you are woken at this stage it feels like you haven’t been asleep at all. You will often experience hypnic jerks which are muscular twitches, typical before the next stage of sleep.

Stage 2 is the next stage. It is still easy to be awoken from this stage though you are unconscious, this is the predecessor of Stage 3.

Stage 3 or slow wave sleep is what we call deep sleep. If you are woken during this stage of sleep then drowsiness and grogginess can be expected. This is also the stage where it is most difficult to wake a sleeping person. You will experience dreams at this stage though not nearly as memorable or vivid as those experienced during REM sleep. Nightmares, night terrors and sleepwalking is most common during this phase.

After 60-90 minutes of non-REM sleep, you will enter the first period of REM sleep. This is characterized by rapid eye movement, muscle paralysis and brain waves similar to the waking state. This first period will be short, around 5 minutes, but the cycle will continue through the night and periods of REM will get longer. The time spent in REM sleep should consist of around 20% of the total.

Dreaming and physiological arousal will be experienced while in REM sleep. Any dreams remembered the next morning will usually have occurred during this stage. It is theorized that the purpose of all this brain activity is to consolidate memories made during the day.

If you’re not getting the sleep your brain and body needs every night, which varies per person but is generally from 6-10 hours than you may not be reaching your full potential. Younger adults, teens and children need more sleep.

A simplified explanation for the purpose of sleep is that the brain needs the REM sleep to analysis and sort what happened during the day and the body needs non-REM sleep to repair the damage that happened during that same day.

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