How We Sleep
We all sleep in different stages. Every night when you go to sleep your brain goes through a pattern and cycle of sleeping. Tests conduction on people’s brain activity while they are asleep showed that there are two basic types of sleep. The two forms of sleep are rapid eye movement (REM) and slow-wave or non-rapid eye movement sleep (NREM). These two states of sleep occur in 90 minute cycles that are repeated five or six times every night. Infants spend about half their sleep time in the REM sleep phase, adults about a fifth, and it is sometimes even less with elderly people.
Non-REM Phase
Non-REM Phase is divided into four phases, accounting for 70 per cent of adults’ total sleep time every night.
STAGE ONE: In the first stage of sleep, that is just as you have started to drift off, your eyes start to slowly roll behind your lids. Breathing becomes more regular and slower. You are less aware of your surroundings, although a whisper could wake you. Often you have the dream-like sensation of falling or jerking, which is enough to arouse you awake. This stage usually lasts for five to ten minutes.
STAGE TWO: This stage accounts for half of the total sleep time. You can easily be aroused from this sleep stage, even though you are even less aware of your surroundings than in stage one. Your brain has small busts of activity which last only for a second or two.
STAGES THREE AND FOUR: In these stages is when you are in a deep sleep. You whole body, including your muscles is very relaxed and you have a slow, regular heartbeat and breathing. Trying to wake someone while they are in these stages is very difficult. During these stages growth hormones are released in our bodies, which encourage growth and development in children, and muscle and tissue repair in adults. A healthy adult will spend about seven per cent of total sleep time in stage three and eleven per cent in stage four.
REM Phase
The REM stage makes up roughly 20-25 per cent of a normal night’s sleep. It is called REM as while you are in this stage, your eyes move about rapidly, flickering and twitching behind your closed eyelids. In this stage you are also temporarily paralysed, except for the muscles needed for basic life-sustaining functions, such as breathing. The blood flow to your brain increases during this time, which is thought to help children’s brains to grow and adult’s brains to repair.
Adults experience REM sleep within 90 minutes of falling asleep and as the cycle repeats during the night, usually either five or six times, you spend a little longer in the REM stage. It is also during the REM stage that dreaming occurs, which lasts between five and thirty minutes. It is unclear exactly why we dream, with some suggesting it is our minds way of dealing with the events of the day, while others say it is how we sort through memories and what we have learnt in order to process it into long term memory, while others suggest that it is just our brain dealing with things that are worth forgetting, overlapping memories that might otherwise clog up our brains.
Why do we Sleep?
There are many theories as to why our bodies require sleep. Many believe that sleep, particularly the REM phase, is important for memory, healing and learning. Also, physical exustion is another reason for sleep, as the body requires time to rest and repair any damaged tissue or muscles. For infants and children, sleep is vital for brain development and growth.
A lack of REM sleep is believed to increase irritability and decrease concentration during the day, while a lack of all four phases of NREM sleep has been shown to leave a person complaining of physical tiredness while awake. After three days without any sleep, a person will normally start to hallucinate, be unable to think clearly, and lose their grasp of reality, as well as show signs of physical fatigue, like headaches and pain.
Sleep Facts
- Narcolepsy is the medical condition for the uncontrollable desire to sleep anywhere.
- The average yawn lasts for six seconds and during a yawn your heart rate can rise as much as 30 per cent.
- Sleepwalkers are called somnambulists, and sometimes they recall their adventures the next day, other times they are completely unaware of what has transpired. Sometimes somnambulists will dress and eat in the middle of their sleep. Sometimes they don’t always go back to their beds to resume their night’s sleep.
- In 1965 17 year–old US high school student Randy Gardner stayed awake for a record of 264 hours, or 11 days. This was part of an experiment conducted by researchers from Stanford University. During the experiment, Randy showed no signs of madness but used loud music and cold showers to stave off sleep. After finally going to bed he awoke after a 15 hour sleep feeling fine.
- Elephants sleep standing up during NREM sleep and lie down for REM sleep.
- Most of what we know about sleep we have only learned in the past 25 to 30 years.
- Scientists have not been able to explain a 1998 study showing a bright light shone on the backs of human knees can reset the brain’s sleep-wake clock.
- Our body’s ‘natural alarm clock’ which enables some people to wake up more or less when they want to is caused by a burst of the stress hormone adrenocorticotropin.
- Studies suggest that women need an extra hour of sleep a night than men.
- In 2000 a camper aged 14 fell 4m off a cliff in Australia after sleepwalking out of his tent. Thankfully, he survived.
