A change in the activity by the way of sleep is visible in all living organisms. Although the change is visible in all living organisms including plants and animals, it is very pronounced in the higher animals.
By the end of the day higher animals lie down, close their eyes and sleep. Most of the lower animals and birds also do the same thing. But insects like ants just stop their movements. They stand still for a while and take rest. Thereafter they proceed with their routine work. Plants also do sleep but its sleep is not so visible as in the case of the higher animals. However, the state of sleep in plants like mimosa and acacia is clearly visible to naked eyes. These plants fold and curl up leaves by the time night sets in. This is how mimosa and acacia send out signals that they are in restive sleep.
Even though each and every living organism undergo sleep, the cause and effect of sleep is a matter of confusion for many.
The living organism is always engaged in some activities or the other during the waking hours. The organism may be stationed idle or it may be engaged in some activity. Whatever be the case, the sensory and the motor centres in the nervous system of the orgasm would be constantly reacting to both the internal and external environs. It means that wakeful hours are really time of hard labour for the organism. The time of hard labour is always followed by labourless and inactive rest which is sleep as everybody knows it. During the rest, however, the living organism would still be active with the functions of breathing, blood circulation and ingestion.
The activities of the organism during wakeful hours result in the loss of vital energy in the nerve cells and the body cells. As a consequence of the loss of energy, the nervous system of the organism reaches a stage beyond which it becomes difficult for the cells to continue their work without getting disorganized. In such situations the nerve cells may even get damaged. Such situations of wear, tear and possible damages normally do not take place. The reason for this is the interference of an inborn reflex action. The reflex action brings in a state of inactivity or inhibition across the nervous system. The inhibition would gradually spread to the body as a whole. This inhibitory state of the physic is called natural sleep. The sleep provides rest to the nerve cells and body cells. The energy lost during wakeful hours is thus recouped.
Sleep is frequently accompanied by dreams. The dreams help prevent sudden waking up from the sleep due to disturbances like body pains, heat, cold, insects, uncomfortable sleeping places and mental agonies. They would reach out to the nervous system through different sensory centres. This may cause sudden waking up from sleep. Such an abrupt waking up is injurious to the extent that the process of recuperation of the lost energy in the nerve cells gets badly affected. The abrupt waking up from sleep is prevented by certain nervous reaction carried out by unconditioned reflexes. The reflex action leads to dramatization of things, matters, events and experiences in the form of visual images. These visual images are called dreams.
The sleep and the dreams are closely related. The dreams help sleep to continue its duty without interruption. Dreams can rightly be called as the closest friend and ally of sleep.
Every body needs sleep. Everybody undergoes sleep. The need for sleep and the way sleep sets in are explained in this article.
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