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YANITINI ARAYAN ESKİ BİR SORU: NİÇİN UYURUZ?

AN OLD QUESTION SEEKING FOR ITS ANSWER: WHYWE SLEEP?

Journal Name:

  • İstanbul Tıp Fakültesi Dergisi

Publication Year:

  • 2007

Key Words:

Keywords (Original Language):

Author NameUniversity of AuthorFaculty of Author
Abstract (2. Language): 
Sleep represents a complicated, reversible process affected from many internal and external factors, and characterized by unconsciousness, selective unresponsiveness and high level organization. Brain is as active as wakefulness during certain stages of sleep. Although our knowledge on sleep physiology is rapidly growing and many of the mechanisms generating sleep are elucidated, the function of sleep, in other words, the answer of the question “why we sleep?” remains its mystery. Although many hypotheses oriented towards sleep function rised, none of them has proven experimental evidence sufficient to persuade sleep researchers. These hypotheses include energy conservation, brain detoxification, brain thermoregulation, tissue restoration and learning and memory consolidation. Following the discovery of REM sleep, critical studies demonstrating a relationship between learning, memory consolidation and that sleep stage were performed. However, learning without sleep seems possible; it is not clear that each sleeping period always followed by a memory consolidation process; and it is not easy to say that in humans, need for memory consolidation is necessary and sufficient for sleep generation. One of the recent attractive hypotheses is synaptic homeostasis which suggests that sleep regulates synaptic weight in brain. According to that hypothesis, synaptic potentiation occurs in cortical circuits of brain during wakefulness; this potentiation correlates with slow wave activity; slow wave activity leads to synaptic reduction which recovers synaptic potentiation. Despite research of fifty years, the only explanation everybody agree with is that: we sleep to overcome sleepiness. Such a point of view is as hopeless as explanations like “we eat to overcome hunger” or “we drink to overcome thirst”. Allen Rechtschaffen, one of the founders of sleep medicine, says for the above explanation that: If this is true, sleep is one of the biggest mistakes that nature made.
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Abstract (Original Language): 
Uyku karmafl›k, yüksek derecede organizasyon gösteren, birçok iç ve d›fl faktörden etkilenen, belli dönemlerinde beyinin uyan›kl›k kadar aktif oldu¤u, geri dönüflümlü bir bilinçsizlik ve seçici yan›ts›zl›k özellikleri gösteren bir süreçtir. Uyku fizyolojisi konusundaki bilgilerimizin h›zla artmas› ve uykuyu oluflturan mekanizmalar›n ço¤unun ayd› nlat›lmas›na ra¤men uykunun ifllevi, di¤er deyiflle “niçin uyuruz?” sorusunun yan›t› gizemini korumaktad›r. Uyku ile ilgili birçok hipotez ileri sürülmesine ra¤men bunlardan hiçbirisi uyku araflt›rmac›lar›n› inand›racak düzeyde deneysel kan›t sa¤layamam›flt›r. Bu hipotezler aras›nda, enerjinin korunmas›, beyin detoksifikasyonu, beyin termoregülasyonu, doku yenilenmesi, ö¤renme ve bellek oluflumu say›labilir. REM uykusunun tan›mlanmas›ndan sonra bu uyku dönemi ile ö¤renme ve bellek pekifltirme aras›nda ba¤lant› oldu¤unu gösteren önemli çal›flmalar yap›lm›flt› r. Ancak, uyku olmadan ö¤renme mümkün görünmekte, her uyku dönemini mutlaka bellek pekifltirmesinin takip edip etmedi¤i bilinmemekte ve insanlarda bellek pekifltirmesine olan gereksinim uyku oluflmas› için gerekli ve yeterli bir nedendir denilememektedir. Son dönemde ileri sürülen ilgi çekici hipotezlerden biri de uykunun beyinde sinaptik a¤›rl›¤› düzenledi¤ini savunan sinaptik homeostasis hipotezidir. Bu hipoteze göre uyan›kl›k süresince beyinde kortikal devrelerde sinaptik potansiasyon olmaktad›r; bu potansiasyon yavafl dalga aktivitesi ile iliflkilidir; yavafl dalga aktivitesi sinaptik büyümeyi eski haline getirecek flekilde sinaptik küçülme sa¤lamaktad›r. Elli y›ll›k araflt› rmaya ra¤men uykunun ifllevi ile ilgili söylenebilen ve herkesin hemfikir oldu¤u tek aç›klama fludur: uykululu¤u engellemek için uyuruz. Böyle bir bak›fl aç›s›, “ac›kmay› engellemek için yemek yeriz” ya da “susamamak için su içeriz” aç›klamalar› kadar umutsuz görünmektedir. Uyku t›bb›n›n kurucular›ndan Allen Rechtschaffen, yukar›daki aç›klama için flöyle söylemektedir: Bu do¤ru ise uyku, do¤an›n yapt›¤› en büyük hatalardan biridir
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