Sleep stages
...etween them is the “percentage of delta”. On the other hand, infants spend most of their time of sleep on stage one and two. The elderly people, the sleep time of third and fourth stage reduces by 10-15% while the second stage increases 5% as you compare to normal adults. NREM sleep initiation starts with the emergency of inhibitory signals from the anterior hypothalamic preoptic nucleus directed caudally toward the brainstem reticular core and posterior hypothalamus. GABA and acetylcholine inhibit histaminergic posterior hypothalamic tuberoinfundibular region. As the Dr Russo mentioned, inhibition of tuberoinfundibular region is key point to fell sleep because it associates with functional disconnection between the brain stem, thalamus, and cortex. REM sleep results from the work of mesencephalic and pontine cholinergic neurons. REM has both tonic and phasic characteristics. Inhibition of alpha motor neurons by clusters of peri-locus ceruleus neurons cause tonic muscle Antonia whis is critical for REM initiation. Phasic rapid eye movements are generated in the paramedan pontine reticular formation and vertical saccades thought to be generated in the mesencephalic reticular formation. Finally, sleep gives your body a rest and allows it to prepare for the next day. The amount of sleep a person needs depends a lot on his or her age. Babies sleep 14 to 16 hours a day. But many older people only need 7 to 8 hours of sleep each night. The sleep also is divided into four stages. First stage is light sleep while second stage is true sleep, but stages three and four are so deep and brain starts producing delta waves. Authors Wade and Tavris’ textbook psychology (2002) has two relevant discussions for this topic. First one, according to text is sleep and wakefulness is most perplexing of all our biological rhythms. The sleep provides relaxing period in which body eliminates the wastes it produced during day time, repair cells, refresh for next day activities. Sleep is necessary for normal mental functioning. If you skip a night’s sleep your normal activities will be affected. As text states, “today we know that during sleep, periods of rapid eye movement (REM) alternate with periods of fewer eye movements, or non-REM (NREM) sleep, in an ultradian cycle that recurs every 90 minutes or so.” The first period lasts from minutes to hours, but the average is twenty minutes. The second period has subdivisions which associate with particular brain wave pattern. Second, when you first sleep and close your eyes, your brain emit bursts alpha waves, which have regular slow rhythm and high amplitude. The person goes through four stages as he or she sleeps deeper and deeper. “Stage 1) your brain waves become small and irregular, and you feel yourself drifting on the edge of consciousness, in a state of light sleep. If you awakened you may recall few visual images. Stage 2) your brain emits occasional short bursts of rapid, high peaking waves called sleep spindles. Minor noises probably won’t disturb you. Stage 3) in addition to the waves characteristic of stage two your brain occasionally emits delta waves, very slow waves with very high peaks. Your breathing and pulse have slowed down, your muscles are relaxed, and your are hard to arouse. Stage 4) delta waves have now largely taken over, and you are in deep sleep and you can’t be a wake”. When you finish these steps, you start from four to three and so forth. As the text states the body is inactive while the brain is extremely active then the term “paradoxical sleep” in this period you are more likely to dream. “Even people who claim they never dream al all will report dreams if awakened in sleep laboratory during REM sleep” (Carole Wade). According the book, REM and NREM sleep continue to alternate throughout the night, with stages three and four as they become shorter and shorter. Finally, if you wake somebody every time they sleep, nothing is going to happen, but if you allow them to sleep for a while they spend much longer time than usual in REM phase. They can’t be aroused easily at this...