By Katie Richardson, Science Editor
When we think of the word ‘sleep’ we immediately relax at the thought of escaping our chaotic lives, and often feel a sense of freedom from the idea of escaping our monotonous daily routines. But do we truly understand the science behind it?
When we think of the word ‘sleep’ we immediately relax at the thought of escaping our chaotic lives, and often feel a sense of freedom from the idea of escaping our monotonous daily routines. Occasionally, we may dream about a scenario or a situation that has persistently been on our minds, or something out of the blue that has never happened before. We then wake up to the sound of a beckoning alarm andare forced to begin another day in our lives, once again. Sleep accounts for one-quarter to one-third of a human’s lifespan. Yet, do we really know what is happening to our body when we slip away into the darkness?
Throughout your time spent asleep, the brain will run through a two-part cycle repeatedly: REM (rapid-eye movement) and non-REM, both of which are different types of sleep. During REM sleep, your eyes move rapidly in different directions. People enter REM sleep within the first 90 minutes of falling asleep and, as the sleep cycle repeats throughout the night, the body will enter REM several times. It accounts for approximately 20-25% of an adult’s sleep cycle, and over 50% of a child’s.
REM sleep consists of the body and brain undergoing several changes, including rapid movement of the eyes, fast and irregular breathing, increased heart rate/blood pressure, increased oxygen consumption by the brain and many more. The first phase of REM usually lasts for 10 minutes, whereas the final stage of REM can last up to an hour. Normally, a state of temporary paralysis is experienced as the brain signals the spinal cord to restrict all movements- this can be seen as a protective mechanism to stop the chance of any injury because of a vivid dream experienced. Generally, throughout REM sleep, the brain is very active, whereas the muscles are very much relaxed. REM sleep can often be referred to as paradoxical sleep.
According to scientific research, many scientists believe that REM sleep can benefit learning, memory and your mood. It can also contribute to the development of the brain in infants. If people don’t get enough of REM sleep, the consequences can be detrimental for the person’s physical and mental health. For example, a lack of REM sleep can lead to the increased frequency of migraines (severe headaches which can affect day to day activities), reducing coping mechanisms during a ‘fight or flight’ situation as the body may take longer to respond and studies have shown that achieving less REM sleep can cause excess weight to build up in adolescents and infants especially. However, a major factor that affects REM sleep is the consumption of alcohol. Studies have shown that the body will take longer than 90 minutes to enter REM, which is a significant delay, causing the whole sleep cycle to be disrupted.
The other stage of sleep (NREM) is described as dreamless sleep and around 80% of our sleep is classified as NREM. This sleep is categorised into three sections- N1, N2 and N3.
N1 consists of an individual becoming drowsy, and is the transition from being awake to being asleep. It isn’t classed as a deep sleep and can often last between 5-10 minutes, which is the shortest out of all sleep types. We can be easily awoken from N1 sleep and can often feel sensations known as ‘sleep starts’ ( a common example is often when we are walking along a path and fall off! ) which is just a sharp muscle contraction.
N2 typically lasts 10-25 minutes and accounts for around 55% of an adults non-REM sleep. During this stage, eye movement and heart rate slows down significantly and the muscles relax even further.
The last stage, N3, is when an individual goes into a ‘deep’ sleep. It is more difficult to wake a person up from this type of sleep due to the fact that the person no longer responds to any stimuli around them e.g certain noises or sounds. This is the stage when the heart rate and the breathing rate is the lowest, with muscle activity further decreasing and no eye movement occurring. This is the most likely stage for sleepwalking/activities, during sleep, such as talking to occur.
So, may I ask the question once more. Did you really know that all of that incredible science was happening whilst you dreamt about your next holiday or relaxing (and certainly stress free) activity? Well there you go. A little bit of science can certainly go a long way. Next time your head hits the pillow, have a little think about what is actually happening inside.
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