Sleep is far more complex than many people imagine and is a period during which our bodies, and in particular or brains, remain surprisingly active. This article looks at the complexities of sleep and the importance of preventing disruption to our normal sleep pattern to stave off insomnia.
Although we might think that our bodies simply shut down and completely relax during sleep, in fact many parts of the body remain surprisingly active. This is especially true of the brain which sends out a constant stream of signals controlling what is known as our sleep cycle.
There are five stages to a normal sleep cycle and, on a good night’s sleep, you will experience all five of them several times in succession. The five stages of sleep are broadly divided in two groups. The first group, which comprises the first four stages, is known as non-rapid eye movement or NREM sleep, while the second group, which contains just a single stage, is referred to as rapid eye movement or REM sleep.
The main difference between NREM and REM sleep is seen in terms of the brains activity. In addition, REM sleep is also characterized by irregular but rapid breathing and heartbeat, a rise in blood pressure and almost no muscle activity.
Throughout a normal night’s sleep you pass through the various stages of sleep several times, but tend to spend about the first third of sleep in the NREM stages and the final third of sleep in a REM stage.
Stage 1 is the stage during which you fall asleep and sees you feeling drowsy and drifting in and out of sleep. Eye movements begin to slow during stage 1 and you start to lose control over your muscles. It is also quite common during this stage to experience sudden contraction and jerking of the muscles.
About half of all sleep is stage 2 sleep during which your brain activity and heart rate slows, your temperature drops and eye movement is reduced to virtually none at all, although there can be occasional short bursts of eye movement.
Both stages 3 and 4 are very similar and, together, are referred to as deep sleep. Brain waves during these two stages are very slow and there is no movement in either the eyes or the muscles.
REM sleep is interspersed throughout the other stages of sleep, which do not necessarily follow a strict numerical sequence, and, in total, represents about a quarter of the time spent in sleep. The first period of REM sleep for example follows stage 1 and lasts for only about ten minutes, while the final period of REM sleep, from which you normally awaken, lasts about an hour.
This repetition of the sleep stages gives rise to the sleep cycles and a normal night’s sleep consists of several sleep cycles. As these cycles continue throughout sleep, REM sleep is also seen to increase. Although it is difficult to control our sleep cycles, there is a great deal that we can do to prevent these cycles from becoming disrupted and thus to ensure sound sleep and, where necessary, to help to cure insomnia.
Stages of sleep have distinct influence on process of learning
Mammalian sleep occurs in two discrete stages, slow wave sleep (SWS) and rapid eye movement (REM) sleep. One of the many ways in which SWS and REM sleep differ is in the level of synchronous firing in the hippocampus.
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Donald Saunders is the author of a number of health-related publications discussing the problems of sleep and giving detailed advice on such things as how to cure insomnia. For more information and additional articles on insomnia please visit Help-Me-To-sleep.com
By Donald Saunders
Published: 1/30/2007
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