Sleep is a complex phenomenon at psycho-physiological level. The sleep can be best defined as reduced state of consciousness or absence of it. In this state, the inability of voluntary muscles, decreased ability react to external stimuli, heightened anabolism are caused. As a result, the energy is conserved. The control of sleep timing, body temperature- fluctuation, release of enzymes is done by Circadian Clock. The brain releases Adenosine, a sort neurotransmitter, which inhibits wakefulness. In all diurnal animals, sleepiness causes release of certain hormones and gradual reduction of body temperature.
But why do we sleep at all? Whether it is necessary for our physical and mental well-being? On the evidences so long gathered, researchers on sleep propounded several theories. We may go through them for a better understanding of sleep. 1) We need sleep to conserve our energy as during sleep we remain still except those involuntary movements. As such, there is 10% reduction in body temperature and demand of calorie in the case of human beings. 2) There is another theory which suggests it is for our survival during the process of evolution because at the times when we are most vulnerable, we go to sleep in a cozy dark nook. But this theory hardly holds from the view of security.3) Sleep gives us an opportunity for repair and rejuvenation of our body and mind. The functions like tissue repair, muscle growth, protein synthesis and release of growth hormone take place during sleep. It also re-enlivens cognitive power of brain. During wakefulness the brain releases Adenosine which is cleared off when we are asleep. So we become alert after sleep. Part of our cognitive process takes place during sleep. While acquisition and recall of information happens during wakefulness, the consolidation of it occurs during sleep. Association of different types of memory with different types of brain waves has also been identified.
So how long we should sleep to keep ourselves fit? It varies with the individuals. Best thing would be determine ones’ own required period of sleep by testing how much sleep much sleep make us fit and alert. It has been proven that inadequate sleep and oversleep are against our health and well-being In this connection, we may cite one example of an experimentation carried out as far back as 1971. Phenomenon is called Yoganidra. Experiment was carried out on Swami Rama while he was in the state of
self-induced conscious deep sleep. electroencephalograph of waves in his brain was recorded. The yogi appeared to enter into various state of consciousness at will. Near the conclusion of the test, he entered deep unconscious sleep though perfectly aware of the experiences during the period, his brain emitting slow delta wave. He could recall experiences during the sleep when he was in wakeful state again. The experiment shows such mastery of consciousness is possible to reduce the requirement of amount of sleep.
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