Sleep and Dreams 1. Describe the cyclical nature and possible functions of sleep. Our daily schedule of waking and sleeping is governed by a biological clock known as circadian rhythm. Each night's sleep also has a rhythm of its own, running from transitional Stage 1 sleep to deep Stage 4 sleep and back up to the internally active REM sleep stage. Stage 1 sleep is characterized by the relatively slow alpha waves and by fantastic images which are like hallucinations. Starting in Stage 3 and increasingly in Stage 4, the brain emits large, slow delta waves. The sleep cycle repeats several times during a normal night's sleep, with periods of Stage 4 sleep progressively shortening and periods of REM sleep lengthening. 2.. Identify the major sleep disorders. Some 10 to 15 percent of adults complain of insomnia in falling or staying asleep. Rarer but more severe than insomnia are the sleep disorders narcolepsy and sleep apnea. People with narcolepsy suffer periodic, overwhelming sleepiness, sometimes at the most inopportune times. The person collapses directly into a brief period of REM sleep. Those who suffer sleep apnea
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