| Sleep : Restorative of Tired Body and Mind
Sleep is one of nature’s greatest inventions and blessings of life. It is a periodic rest of the body which is absolutely essential for its efficient functioning. It has been called " most cheering restorative of tired bodies. " Sleep is the indispensable condition to the recuperation of energy. We go to bed fatigued and get up refreshed. Sleep repairs the wear and tear of the body and mind incurred during waking hours. Nothing is so restorative to the nerves as sound and uninterrupted sleep. Sleep is thus a vital element in a total way of life. It is a basic need in man’s mental as well as physical life. During sleep most of the functions of the body are carried on at the lowest level possible in health. Heat production is from 10 to 15 per cent below the basal level. The mechanism regulating the body temperature are less sensitive than in the waking state and are depressed by 0.5 to 1.0 degree F. The rate of the heart is reduced by 10 to 30 beats per minute and a decline in blood pressure of about 20 mm occurs in quiet restful sleep. The urine volume is considerably reduced, but its concentration in solids is increased. The tone of all the skeletal muscles is lessened. The eyes are usually rolled upward and the pupils constricted. Loss of sleep exerts seriously detrimental effects upon the nervous system. Long periods of wakefulness may cause profound psychological changes such as loss of memory, irritability, hallucination and even schizophrenic manifestations. During the last World War, prisoners in Nazi concentration camps who kept awake for days by strong lights and blaring wireless sets, collapsed. Sleep versus rest For correct living, it is essential to differential between sleep and rest. At rest the body is disturbed by all exterior noises ; but in sleep it is screened from them by partial loss of consciousness and also by what is called " dream protection. " One useful purpose of the dream is to convert outside noises that might awake the sleeping person, into fantasies that do not disturb him. During rest the limbs are normal, but in sleep they swell. Blood flows from the brain, distends the arteries, and makes the limbs bigger. IN sleep more muscles are relaxed than in rest, though the sleeping person changes his position about 35 times in one night, without knowing it. Many organs which work during rest suspend their activities in sleep. Thus the recouping value of sleep is much more than that of rest or simple lying down. Theories of sleep Many theories of sleep have been advanced to explain the temporary loss of consciousness which we know as sleep. The oldest theory is that sleep is induced by a reduction in the blood supply to the brain or at least to conscious centres. This is known as ischemic theory. Even the ancient Greek physicians were aware that the carotid artery was in a way concerned with the onset of sleep. The name itself expresses this belief. The Greek word ‘ Karotides’ for carotid arteries is derived from karoo which means ‘put to sleep.’ In modern times, the drowsiness after a meal, presumably due to the diversion of blood from the brain to the digestive organs, is cited in support of the ischemic theory. Another important theory about sleep is the chemical theory. As a result of experiments in the metabolism of sleeping subjects, it is considered that the fatigue inducing sleep may be a mild form of blood poisoning or toxaemia. This " poisoning" is believed to be brought on by the expenditure of energy during the waking hours. According to this theory, every contraction of a muscle and every impulse passing through the brain or the nerves breaks down a certain amount of tissue. The debris from broken down tissue is then thrown into the bloodstream. In the waking state, much of the waste from broken down tissue is got rid of through the natural eliminating processes of lungs, kidneys, bowels and skin. |
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