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brain and recuperates the necessary elements for normal functioning of the life system. There are some physiological changes to effect this: (a) During sleep, Adreno-Corticotropic hormone (ACTH) is produced in large amounts to accommodate the stress of the day. (b) During quite sleep, a growth harmone (somatotropin) is produced in large amount leading to proper growth of the system.
Sleeping is a process where mind does not operate, the normal consciousness also does not seem to function, the physical activities get inactivated but the brain remains partly active. Sleep is a state of brain and consciousness.
Studies on sleep indicate that it is a rhythmic process. Its centres are located in the hind part of the brain in its thalamic and hypothalamic parts. It also seems that the sleeping and waking systems partially occupy the same structures so that low-frequency stimulation has been found to bring sleep. The presence of hypnotoxin in cerebrospinal-fluid also causes sleep. The production of amines like sero-tonin and catecholamines also induce quite and active sleep. Moreover, there are many sleep retarding compounds also like (i) reserpine, (ii) gamma butyrolactone, (iii) 5-hydroxy-tryptophan, (iv) malamide etc. They are said to inhibit REM sleep.
It has been observed that there are two kinds of sleep - (1) active or Rapid-eye-movement (REM) sleep and (2) quiet-sleep. There are dreams in active sleep which may also involve somnambulism. There are repetitive five stages in normal sleep. These have been identified with the EEG studies through electrical stimulation :
(1)
First Stage
(2)
(3)
(4)
Second Stage (drowsy state)
Third Stage (light or medium sleep)
Fourth Stage (deep sleep)
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Relaxing of muscles, slackening of breathing and heart beat, steady alpha waves in the brain, drowsiness appears, easy wake-up. Sleeping is deeper, alpha brain waves become spindular, eyes begin rolling, wakeup with some difficulty, delta-waves appearing.
Body gets more relaxed, tension eases, brain wave pattern changes from alpha to delta (14 cycles/sec), declining of heart beat etc, further, light or medium sleep, wake-up little more difficult, wave frequency changes, lower consciousness.
Deep-sleep, bed-wetting, sleep-walking and sleep-talking may occur during this stage,
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