We all know what sleep is; on average, we spend approximately one-third of our lives asleep. It is vital to good health. But how much more do we understand what happens when we are asleep? Even today, we do not understand every aspect of this behaviour. However, what we do know is fascinating.
Sleep is a very complex. It involves a number of parts of the brain and bodily functions. However, we understand much better the mechanics of sleep and what stages there are in the sleep cycle. Our physical, emotional and mental health are all involved in sleep. And if we go without sleep for an extended period, it leads to many serious health problems.
The changes begin within a few minutes of falling asleep. For example, our temperature begins to drop, our heart rate and breathing pattern slow along with our brain activity. So it is no surprise to learn that our energy requirements are reduced during sleep.
There are four recognised stages to a sleep cycle and these cycles can last from 70 minutes to up to 120 minutes. The first three stages are known as the non-REM stages or NREM. The fourth stage is the REM stage. The REM stands for rapid eye movement, but more of that later.
Stage 1 is known as N1 and begins soon after you fall asleep. It only lasts between one and five minutes, so we can look at it as the transition or introduction to Stage 2.
Stage 2 is where the mind and body slow down and this process can last anything from ten minutes to one hour. We are in a light sleep during this stage so it is easier to wake someone up from it.
Stage 3 is where we reach deep sleep. It can last for between 20 to 40 minutes. The brain and body are now much slowed down and if an MRI scan is taken of the brain and compared to the same brain when awake, they are very different. This stage is important as we think this is where the mind and body are able to recuperate from all it is asked to do when they are awake.
Stage 4 is the final stage and is the only REM stage. It is characterised by noticing the eyes are moving rapidly under the eyelids. With an MRI scan, we would now see quite an increase in brain activity. However, if we neglect the eyes and our breathing, the rest of our systems experience a period of temporary paralysis. It is often believed that REM sleep is when we dream. This is partially true as our most intense dreams take place during this stage. But dreaming can take place during the other stages as well. It is also believed that the REM stage is essential to help the brain to continue to function. Memory and learning are also said to benefit during this stage. The REM stage usually lasts longer as the cycles progress. They range from ten minutes to one hour.
We usually need less sleep as we get older. A newborn infant needs between 12 to 16 hours of sleep a day. At junior school age, a pupil needs between 9 to 12 hours of sleep. A teenager needs 8 to 10 hours and an adult needs around 7 hours of sleep. I hope you are still awake after reading this.
John Pullen 