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Insomnia & sleep Physiology, Sleep Deprivation & Disorders

Home > Treatment Articles > Insomnia > Insomnia and the Physiology of Sleep

You and I function according to a natural cycle that repeats itself every 24 hours. The name of this cycle is the circadian rhythm and it controls our sleeping cycle and our waking cycle.

Interestingly, when it gets dark, the cells in the retina of the eye send a message directly to a special part of our brain. The pineal gland then produces the hormone melatonin and this causes a drop in our body temperature and sleepiness. At the same time, there is a reduction in those chemicals in our body which are responsible for arousal.

Most people are then ready for sleep.

This sleep is characterized by two distinct states, non-REM sleep and REM sleep. Both states alternate in 90 to 110 minute cycles while a normal sleep pattern has 4-5 cycles so you can see how this makes up our roughly 8 hour night’s sleep. However these cycles of sleep have been compared to going up and down a stairway.

Non REM sleep which takes up about 75% of the sleep cycle has 4 stages ranging from light dozing to deep sleep.

  • Stage 1 is the dozing stage and a period of very light sleep when we start to relax. It is during this stage that you may experience the sensation of falling and jerk suddenly into wakefulness which is called a hypnic jerk.
  • Stage 2 is characterized by a lack of eye movements and a time of light sleep. You could still be woken up fairly easily.
  • Stage 3 is when deeper sleep is experienced and you would become more difficult to wake up.
  • Stage 4 is a time of very deep sleep and if you are woken during such deep sleep, you will probably feel sleepy and disorientated for several minutes.


The deep sleep you experience in stages 3 and 4 is called delta sleep and it is the most restful kind of sleep.

REM sleep (Rapid Eye Movement) takes up about 25% of our sleeping cycle.

REM sleep is when most dreaming takes place along with periodic eyelid fluttering, muscle paralysis and irregular breathing. At this time, the brain blocks signals to our body’s muscles so that we remain immobile during our dreams and do not thrash about and act them out.

Sleep is a very necessary and important function in our daily lives and essential to our physical and emotional well being. Without enough daily sleep, our ability to perform even the simplest task can be severely reduced. Sleep restores our body and mind, allowing the body to rest and the mind to do a lot of sorting out such as organizing our long term memory, absorbing new information as well as repairing and renewing tissue, nerve cells and even biochemicals.

The longer you stay awake, the more sleep you need.

So if you are awake for 36 hours, you may well need to sleep for 18 hours to catch up again thereby allowing the body to reverse the effects of sleepiness by sleeping. The body reacts to a lack of sleep by having daytime drowsiness so that you are inclined to go to sleep early or to sleep in late. The ideal amount of sleep you need is the amount needed to feel refreshed and well rested in the morning so that you stay alert all day.

You can therefore see how debilitating insomnia can be and how we need to find out the reason or reasons for any insomnia we may be suffering as well as treating the symptoms of the condition itself.