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Pharmacy Links

WHY SLEEP?

11/03/09

Sleep is a fascinating biological function which we all experience. In fact, one-third of our lives is spent in sleep. Most of us take it for granted that we fall asleep at night and wake up the next morning. We do this night after night, and we do this from the day we enter this earth to the day we depart. However, have you stopped and asked what sleep actually is and why we need to sleep at all?

We have all experienced the fact that after a good night’s sleep we are refreshed and appear to function better than after a restless night. The exact nature of this is not fully understood. Sleep is not unique to man. Nearly all species of the Animal Kingdom sleep. But the amount of sleep in animals varies a great deal between different species. Gorillas sleep 14 hours a day, elephants only 2.

Evolution theory

The first explanation of why we need to sleep is coherent with the theory of evolution and survival. Hibernation, which is like a very deep sleep in winter for some animals, has been studied extensively by biologists. It is an adaptive survival mechanism enabling certain animals to survive long snowy winters; without it, many of these animals would face extinction. The hibernating animals do not need food during the winter months, at a time when food may be scarce or unavailable. Just before winter comes, they have built up a great deal of body fat. When winter arrives, they automatically go into extremely low activity and so can survive solely on their fat reserves. There is very little movement, the body temperature is very low, the metabolism is minimal, and the breathing is slow and shallow. The brain waves of these hibernating animals are nearly silent and are in distinct contrast to those of sleep. Normally, during hibernation, the animals cannot be aroused, even if given a good shake.

Hibernation has been studied in laboratory conditions. The animals are kept inside in the warm with plenty of food throughout the winter. However, they still go into hibernation, as if there is a need for them to do so. Hibernation is an innate mechanism in these animals; they do not have to learn how to hibernate. Hence the mechanism could have been handed down from one generation to i the next through the genes.

What about sleep? Sleep is distinct from hibernation. This is shown by the different brain wave pattern and the fact that an animal can always be aroused from sleep but not from hibernation. Sleep is another evolutionary adaptation to survival. The earth e every 24 hours and any one point on the surface is i nearly half of this time. Man has been walking on the ?planet Earth for over a million years. Remember that artificial light such as candles, oil lamps, and electric lights are inventions only of the last thousand years. During the long dark night, primitive man had noyjing to do. In fact it could be dangerous to move around in the dark. Man could injure himself easily by tripping over in hrough meeting some vicious animal. Hence he withdrew , stayed put,closed his eyes, and slept.

The need to sleep at night not only withdraws us from a dangerous environment, but also allows us to rest and restore our energy. Sleep is an innate biological hibernation, and has been studied under laboratory conditions. Even if the room is continuously brightly lit without the cue of what time of day or night it is, we still feel the need to sleep once every 24 hours or so. Here, the need to sleep is very similar to the need to hibernate—an evolutionary adaptation for survival.

Chemical theory

Another possible explanation of why we sleep is the chemical theory.We are all aware of the fact that certain chemical substances induce sleep; we have all heard of sleeping I pills. When we take a sleeping pill, the drug is absorbed into the brain.When the drug wears off and is eliminated from the body, we wake up.

Is there a sleep-inducing, naturally occurring chemical in the body? Also, does this chemical accumulate in the day like a waste product from our metabolism and require elimination? When the chemical reaches a certain threshold, does the brain become drugged and cause us to fall asleep? Whilst asleep, is this chemical eliminated from the body, causing us to wake up refreshed? A French scientist in 1913 called this hypothetical chemical sleep poison or hypnotoxin.

The answers are all no. This is shown in the example of Siamese twins. Siamese twins are two twins born together with some parts of their bodies attached. They share the same blood circulation. It is observed that one twin can be wide awake whilst the other is fast asleep. If there is a chemical in the blood causing sleep, then the two twins should be waking and sleeping at the same time. This clearly demonstrates that ‘natural sleep’ is not due to a chemical or a drug circulating in the blood. On the other hand, if one twin is given an appropriate dose of sleeping pill, after this is absorbed into the blood the two twins sleep at the same time. This shows that sleep induced by sleeping pills is very different from natural sleep, and the chemical theory is unable to explain why we need to sleep.

However, in spite of this, there is still considerable research taking place to examine the possibility of the presence of hypnotoxin. Claims were made that extracts of spinal fluid from sleep-deprived animals when injected into waking animals would induce sleep. US scientists called this substance in the spinal fluid factor S (5 for sleep) and Japanese scientists called it sleep-promoting substance or SPS. Sleep-deprived animals were used for the source of this substance as it was believed that factor S or SPS accumulated greatly in these animals, since only sleep could eliminate it.

Biological theory

Now, what is the biological benefit of sleep? One suggested benefit is growth. We all have a small pea-like structure at the base of the brain called the pituitary gland. This secretes growth hormone and is responsible for growth and normal development of the body. It is now known that growth hormone is secreted in a greater amount during deep sleep. There are reports that in some victims of child abuse the children are afraid to sleep or wake up too often at night to have any deep sleep; these children do not grow much. Their dwarfism results from an insufficient secretion of growth hormone.

Once they are removed from their homes and put into a more loving environment their sleep improves and their growth becomes more rapid, as if they are catching up on lost ground. Of course, one cannot overlook other factors such as nutrition, exercise, and so on. We now know that children need much more sleep than adults. In fact, the older we are, the less sleep we need. Is this because we need less growth hormone as we become older and consequently less sleep?

Dream theory

Another possible explanation of why we need to sleep is perhaps a psychological one. When we are sleeping, we all dream. Dreaming has a restorative function. We act out and experience some of our frustrations and anger during dreams. When we wake up the next morning, we have forgotten our dreams. This forgetting is important, as it allows us to forget our frustration and anger at the same time. Dreams are like a psychological filter, filtering out the worries that accumulate during the day. Sleep laboratories have demonstrated that when we are dreaming all the big muscles of the body are totally relaxed. This may be the only time that the body muscles are ever completely relaxed.

Another recent discovery in dream study is the occurrence of a male erection, which is discussed in chapter on Sex and Dreams. It has been observed that whenever a man dreams his penis is erect, no matter what sort of dream he is having. This dream erection occurs in all age groups and I believe this to be important for the proper development of the penis. Hence, at least for men, dreams are very important.

Neurone theory

A television documentary recently reported an unusual case of insomnia in England. Loughborough University advertised for people who thought they did not need to sleep to come forward to join in a sleep research study. So people who were short sleepers volunteered to be tested under laboratory conditions. At night they were allowed to lie in bed to rest and their brain waves were monitored continuously. There was a man who claimed that after an accident causing head injury a few years earlier he did not sleep at all. He also claimed that he was functioning normally and did not feel worried when he was lying awake. Brain wave recordings showed that he slept only four minutes during the three day study.

The study findings suggest that perhaps the brain is programmed to sleep periodically. The man who did not have the need to sleep after the head injury may have had his brain reprogrammed in such a way that sleep was no longer required. Maybe in hundreds or thousands of years from now we will be able to reprogram the brain so that we will have the choice of not having to sleep at all. There is a Chinese saying, ‘Life is not as long as it seems, as half of it is spent sleeping’.

It is possible that there are other biological functions, yet to be discovered, which only happen in sleep.