Types and the stages of sleep

Do you know there are four stages of sleep and there are some certain way to measure it  The appearance of the electrical brain waves varies according to whether we are brightly alerts quietly relaxed, especially if our sound asleep. When we are awake and relaxed, especially if our eyes are closed, we often have brain rhythms at about 10 waves per second; these waves we call the alpha rhythm.

The stages of sleep

The alpha rhythm disappears if we face a sudden and a new challenge in life, particularly if the eyes are open at the same time. The rhythm also disappears when we become drowsy and it then becomes replaced by rather slower waves. We call the brain waves of drowsiness,

Stage 1: sleep, If we are really going to sleep, then we go into

Stage 2: sleep, in which the electrical brain waves are quite a lot slower and in which some distinctively shaped waves called spindles make their appearance.

In young people, and especially in the early part of the night, stage 2 will progress to brain waves with more and more large slow waves and we call this  pattern

Stage 3: or, with even more slow waves,

Stage 4: All these four stages are termed ‘orthodox’ sleep. Interspersed with orthodox sleep is another phase of sleep we have not yet mentioned, namely ‘paradoxical’, or rapid eye movement (REM), sleep.

Orthodox and paradoxical sleep

Paradoxical and orthodox, or non-rapid eye movement (NREM), sleep alternate throughout the night, governed by the 100-minuted ultrafine rhythm. Normally, about 20 per cent of sleep is paradoxical and 80 per cent orthodox.

The recorded brain waves of paradoxical sleep and in fact resemble those of the deeper stages of orthodox sleep and in fact resemble those of drowsiness.

The tell-tale movements of the eyes can also be detected using the EEG because the machine can be set up to record movement of the eyeballs as well as electrical brain rhythms.

Types of sleep

Babies spend a great deal of their sleeping life in paradoxical or rapid eye movement (REM) sleep.

However, the existence of this kind of sleep was first observed without the aid of an EEG simply be watching babies and seeing that for some periods during their sleep their eyes were jerking hither and thither for minutes on end.

When paradoxical sleep was first being described, it was not then realized that it was different kind sleep, and it was thought of as light sleep with dreaming.

Later it was found to be accompanied by the greatest muscle relaxation, as if it were the deepest sleep, at the same time as being the lightest sleep hence the name ‘paradoxical’.

Many journalists fostered the idea that it was ‘dreaming sleep’ and the addition notion that we know to be untrue, and we now realize that we can dream during all other stages of sleep, though we recognize that the richest dreams are experienced during paradoxical sleep.

Types and the stages of sleep

This lines are sections from an EEG print-out. Each of the bottom four brain-wave patterns is distinctive of a particular stage of sleep.

Really it is wrong to think of either paradoxical or orthodox sleep as being the deeper or lighter. In stage 4 orthodox sleep we are most difficult to awaken; but in paradoxical sleep our muscles are at their most relaxed, so that you could say that either of these types of sleep is the deeper, depending upon what you think is the more important.

The fact is that they are just different. In paradoxical sleep we have twitching movements, not only of the eyeballs, but of many parts of the body.

Cats or dogs will twitch their tails, their whiskers, and the tips of their paws so that we will say, ‘that dog’s dreaming’.

We too twitch our faces; and our breathing, heartbeat and blood pressure become irregular; a remarkable paralysis affects most of our body except for those momentary twitches; and the blood rashes through the brain at a faster rate than during orthodox sleep.

During paradoxical sleep too, whether sexual dreams are being experienced or not, in men the penis becomes erect, and in women the blood flows more rapidly around the vagina, while the nipples become erect.

The paralysis of the muscles in paradoxical sleep forms the basis for the occasional experience that any of us can have of waking from a dream and momentarily feeling unable to move.

Types and the stages of sleep

Orthodox or NREM sleep alternates with paradoxical or REM sleep throughout the night. Taking sleeping drugs or alcohol will alter these proportions.

It seems likely that paradoxical sleep is actually the oldest kind of sleep in evolutionary terms, for it is a time when the brain no longer keeps the body’s temperature constant by making muscles shiver and it seems to be the sleep of our ancient cold-blooded ancestors.

Orthodox slow-wave sleep is in some ways certainly more restorative (it is the stage when growth hormone is released into the blood-stream); and is probably a necessity for warm-blooded creature like ourselves, who expend vastly more energy while we are awake than do cold-blooded reptiles.

In the course of evolution, some warm blooded animals have evolved a particular kind of orthodox sleep, with very slow electrical brain waves, in which their body temperature falls even more than it does during our sleep, down to very low levels: and they then expend hardly and energy in keeping themselves alive. This is hibernation.

Does it matter if you don’t get enough paradoxical sleep?

We are not able to say that for human beings the one kind of sleep or the other is in any way better, and there is no evidence that lack of paradoxical sleep will leave us unrefreshed. We just need sleep, and we need both kinds of sleep.

The proportions or amounts that we get on each are beyond our own control. Drugs will change, then proportions, and most drugs, such as leaping drugs, reduce the time spent in paradoxical sleep.

Although this reduction is a departure from normal, it does not mean that we are going to come to harm from normal, it does not mean that we are going to come to harm as a result. Do not believe anybody who tells you that you ought to have more paradoxical sleep with its rapid eye movements.

Left to itself, the brain can look after its own needs, so long as we do not insult it too much by keeping grossly irregular hours, or by excessive indulgence in alcohol or other drugs.

Many disturbing misconceptions have arisen over the years about the need for the different types of sleep and especially about their connection with dreaming. Dreams and nightmares are the subject of the next chapter, in which we will be attempting to dispel some of the myths.

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