Everybody has a natural rhythm of sleeping and waking, that is based on his or her life daily rhythm cycle. About one third of a person’s life is spent in this state of near unconsciousness. However a sleeper is still aware of some aspects of his surroundings, such as noises, and some parts of his brain and body are less affected than others.
It is not known what mechanism triggers off sleep. Different theories suggest that:
It is due to reduction in the amount of oxygen reaching the brain.
A reduction in the number of impulses reaching the conscious centers.
A chemical process in the brain.
The repeated promptings of the conditioned response
It is also known that, there are certain cell groups, through out the brain, which bring about sleep when stimulated, and others, that cause a sleeper to wake.
There are two stages of sleep. Orthodox and parodoxical sleep. Orthodox sleep is characterised by a fall in the heart rate, the blood pressure and the metabolic rate. Breathing is regular but slow. In light orthodox sleep, movement may occur, up to 40 changes in position a night. But in deep orthodox sleep, both muscles and brain are in their most relaxed and there is no movement. The electrical activity of the brain becomes markedly different from the waking state. It is during this deep stage, that there is a rise in the growth hormones, and protein production is stepped up. The body repairs itself and dead cells are replaced.
Paradoxical sleep/Rapid Eye Movement (REM) is the stage in which dreams occur. Breathing and heartbeat become irregular, and there is rapid eye movement (REM), behind the closed eyelids. The electrical activity of the brain resembles that of the waking state. Although movement may occur, the muscles are often as relaxed as in orthodox sleep, and the sleeper is just as difficult to wake.
The sleeper begins with light orthodox sleep, until after about 20 minutes he enters into deep orthodox sleep. The first period of deep sleep is the longest of the night, lasting about an hour. The sleeper then moves through light sleep to the first period of Paradoxical sleep about one and half hours after falling asleep. During a typical night’s sleep of 7 to 8 hours, this cycle recurs about 5 times.
However as the night progresses, the periods of deep sleep become shorter, until after about 3 hours the stage of deep sleep is not reached at all. The periods of light and paradoxical sleep become correspondingly longer from 10 to 30 minutes in the early part of the night to up to an hour at the end of it. Normally, paradoxical sleep takes up about 20% of an adult sleeping time and 50% or more of a baby. I took time to explain the details and physiology of sleep so that next Sunday when I discuss disorders of sleep it would be understood.
The need for sleep is encapsulated in the scientific fact that people die more quickly from lack of sleep than they do from lack of food. A person kept awake for long periods becomes increasingly disorientated, and both mentally and physically exhausted. After 10 days of total sleep deprivation, death usually occurs.
But it seems we do not sleep just because the body needs to rest. Lying down would be adequate for that. In fact, the body shifts regularly during sleep, to prevent its muscles seizing up, and if we do have to do without sleep for several days, our automatic body processes can go on functioning in a fairly steady way. The body does get rest during sleep – but it does not seem to be sleeps special purpose.
What cannot go on in a normal way with sleep is the brain. Lack of sleep brings irritability, irrationally, hallucinations, growing mental derangement and finally insanity, before death occurs. This and the steady way body processes carry-on, suggest that our feelings of physical exhaustion are also produced by the brain in its unwillingness to go on controlling the body.
Sleep then “rests” the brain. But the brains electrical activity carries on during sleep, it certainly does not switch off. So whatever special needs the brain desires are being satisfied.
To the question of why dreams occur during sleep, as asked by some of my respondents, a famous experiment gave the answer. One group of sleepers was woken whenever their REM sleep began, so preventing them from dreaming. They soon showed all signs of mental disturbance. Another group, woken equally, but only in other stages of sleep, hardly suffered. So sleep occurs because the brain needs to dream, and when sleep is prevented the hallucinations which eventually occur are in roughly the same pattern as dreams would occur in sleep.
Most of the unborn child’s day is spent sleeping. After birth, the amount of sleep needed gradually declines with growth. A new born baby sleeps on average 16 hours a day, though he may be deeply quiet at other times. A 6-year-old 10 hours. A 12-year-old 9 hours. An adult 7 hours 20 minutes. But there are wide variations around these figures. Some babies sleep 10.5 hours, others 23 hours. Some adults sleep 14 hours, others only 2 to 3 hours.
The need for sleep is highly personal, and it is not known why. It does not matter one’s sex or one’s intelligence or the amount of exercise one gets. However, it is thought that many people try to get too much sleep, they have insomnia or use sleeping pills, because they fail to realize that their need for sleep is relatively low. Whether an adult’s need for sleep declines with age is uncertain.
The tradition is that those over 65 need on average only 5 hours a night. But recent evidence has suggested that needs are constant from 30 on.
Insomnia (sleeplessness) may be occasional or chronic. Sometimes it is not really sleeplessness at all; the person has slept, but not realised it, because it was so restless and unrefreshing. Causes of occasional insomnia include
Feeling cold or using too light bed coverings.
Indigestion and abdominal upset.
Excessive fatigue.
Excitement
Nervousness.
Worry.
Pain or illness.
Regular insomnia may manifest due to difficulty in breathing when lying down as in heart or lung disorder.
Bad food habits, especially eating or drinking tea, coffee, too late in the evening.
A need to urinate during the night.
A noisy, airless, or overheated bedroom.
Lack of exercise during the day.
Trying to sleep more than you need.
And psychological factors – overwork, worry about work, anxiety, emotional upset and depression.
But the main cause of any insomnia whether occasional or regular, is simply the fear that one is not going to sleep. Always be medically guided.
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