Beyin, omurgal\u0131larda, kafatas\u0131 bo\u015flu\u011funun i\u00e7inde yer alan ve merkez sinir sisteminin \u00f6n b\u00f6l\u00fcm\u00fcn\u00fc olu\u015fturan, yo\u011funla\u015fm\u0131\u015f sinir dokusu. Duyular arac\u0131l\u0131\u011f\u0131yla al\u0131nan verilen birle\u015ftirip b\u00fct\u00fcnleyerek, bu uyar\u0131lara yan\u0131t niteli\u011findeki hareketleri y\u00f6neten, bu nedenle temel i\u00e7g\u00fcd\u00fcsel etkinliklerde \u00e7ok \u00f6nemli bir rol oynayan beyin, \u00fcst\u00fcn yap\u0131l\u0131 omurgal\u0131larda ayn\u0131 zamanda \u00f6\u011frenme merkezidir. Omurgas\u0131zlar\u0131n beyni, bir dizi sinir kordonunun \u00f6n ucunda k\u00fcmelenmi\u015f sinir h\u00fccrelerinden, omurgal\u0131lar\u0131n beyni ise omurili\u011fin \u00f6n b\u00f6l\u00fcm\u00fcn\u00fcn iyice geni\u015flemesinden olu\u015fur. Geli\u015fmemi\u015f omurgal\u0131lar\u0131n beyni, b\u00f6yle bir geni\u015fleme g\u00f6stermedi\u011finden, daha \u00e7ok bir boruyu and\u0131r\u0131r; bu hayvanlar\u0131n beyni ile daha \u00fcst\u00fcn yap\u0131l\u0131 omurgal\u0131 embriyonlar\u0131n\u0131n erken geli\u015fme evrelerindeki beyni aras\u0131nda olduk\u00e7a b\u00fcy\u00fck bir benzerlik g\u00f6ze \u00e7arpar.<\/p>\n
Geli\u015fmemi\u015f omurgal\u0131lar\u0131n beyninde \u00fc\u00e7 b\u00f6lge ay\u0131rt edilir: Arka beyin ya da art beyin (rombensefal), orta beyin (mezensefal) ve \u00f6n beyin (prozensefal). \u00dcst\u00fcn yap\u0131l\u0131 omurgal\u0131larda, embriyonun geli\u015fmesi s\u0131ras\u0131nda beyin \u00f6nemli de\u011fi\u015fiklikler ge\u00e7irirse de, bu \u00fc\u00e7 b\u00f6lge aras\u0131ndaki ayr\u0131m sonuna de\u011fin korunur. Ancak, embriyonun geli\u015fmesi s\u0131ras\u0131nda orta beyin~oldu\u011fu gibi kal\u0131rken \u00f6n beyin ve arka beyin iki\u015fer alt b\u00f6l\u00fcme ayr\u0131ld\u0131\u011f\u0131ndan, beyinde be\u015f b\u00f6lgeli bir yap\u0131 ortaya \u00e7\u0131kar: Arka beyin, beyinci\u011fi olu\u015fturan metensefal ile so\u011fanili\u011fi (so\u011fanc\u0131k ya da omurilik so\u011fan\u0131) olu\u015fturan miyelensefal b\u00f6lgelerine ,ayr\u0131l\u0131r; \u00f6n beyinden ise, bey\u0131n yar\u0131mk\u00fcrelerini olu\u015fturan telensefal (b\u00fcy\u00fck beyin) ile talamus ve hipotalamusu olu\u015fturan diensefal b\u00f6lgeleri do\u011far. Beyni, beyin yar\u0131mk\u00fcreleri(*) ve beyin sap\u0131(~) olmak \u00fczere iki b\u00fcy\u00fck b\u00f6l\u00fcm halinde incelemek anatomi a\u00e7\u0131s\u0131ndan b\u00fcy\u00fck kolayl\u0131k sa\u011flar. Bu incelemede, diensefal (talamus ve hipotalamus), mezensefal (orta beyin), metensefal (Varol k\u00f6pr\u00fcs\u00fc ve beyincik) ve miyelensefal (so\u011fanilik) b\u00f6lgeleri beyin sap\u0131 i\u00e7inde say\u0131l\u0131r. Beyin sap\u0131 i\u00e7indeki olu\u015fumlar\u0131n en \u00f6nemlileninden biri olan ve embriyondaki arka beyin b\u00f6lgesinden t\u00fcreyen beyincik, dengenin ve kas hareketlerindeki e\u015fg\u00fcd\u00fcm\u00fcn sa\u011flanmas\u0131ndan sorumludur. So\u011fanilik ise, omurilikten gelen sinyalleri beynin daha yukar\u0131daki b\u00f6lgelerine iletir; ayr\u0131ca kalp at\u0131\u015f\u0131 ve solunum gibi otonom sinir sistemi i\u015flevlerini y\u00f6netir.
\n \u00dcst b\u00f6l\u00fcm\u00fc, embriyonun ilk evrelerindeki ve geli\u015fmemi\u015f omurgal\u0131lardaki g\u00f6rme \u00e7\u0131k\u0131nt\u0131s\u0131ndan t\u00fcremi\u015f olan orta beyin, bal\u0131klarda ve amfibyumlarda duyulardan gelen verilen birle\u015ftirme merkezidir. Ku\u015flarda bu i\u015flevi orta beyin ve \u00f6n beyin birlikte \u00fcstlenir. Memelilerde ise orta beyin iyice k\u00fc\u00e7\u00fclm\u00fc\u015ft\u00fcr ve daha \u00e7ok \u00f6n beyin ile arka beyin aras\u0131ndaki ba\u011flant\u0131y\u0131 sa\u011flar
\n Diensefal b\u00f6lgesinden do\u011fan talamus, so\u011fanilik ile beyin yar\u0131mk\u00fcreleri aras\u0131nda, demiryollar\u0131ndaki makas ya da r\u00f6le istasyonlar\u0131n\u0131n i\u015flevini \u00fcstlenir. Hipotalamus(*) ise, cinsel g\u00fcd\u00fcleni, ho\u015flanma, a\u011fr\u0131, ac\u0131kma ve susama duyumlar\u0131n\u0131, kan bas\u0131nc\u0131n\u0131, v\u00fccut s\u0131cakl\u0131\u011f\u0131n\u0131 ve i\u00e7 organlara ili\u015fkin \u00f6b\u00fcr i\u015flevleri denetleyen \u00f6nemli bir merkezdir. Ayr\u0131ca hormon salg\u0131s\u0131n\u0131n d\u00fczenlenmesinde de \u00f6nemli g\u00f6revler \u00fcstlenir; hipofiz bezinin \u00f6n b\u00f6l\u00fcm\u00fcn\u00fcn salg\u0131s\u0131n\u0131 uyaran hormonlar\u0131 ve bu bezin arka b\u00f6l\u00fcm\u00fcnde depolan\u0131p salg\u0131lanan oksitosin ve antidi\u00fcretik hormonlar\u0131 \u00fcretir.
\n Soyolu\u015f ve embriyonolu\u015f evrimleri s\u0131ras\u0131nda koku \u00e7\u0131k\u0131nt\u0131s\u0131n\u0131n bir par\u00e7as\u0131 olarak geli\u015fen telensefal, insan beyninde \u00e7pk daha karma\u015f\u0131k i\u015flevlerden sorumludur. \u0130nsanda ve \u00f6b\u00fcr geli\u015fmi\u015f omurgal\u0131larda bu b\u00f6l\u00fcm, k\u0131vr\u0131ml\u0131 bir bozmadde k\u00fctlesi olu\u015fturacak bi\u00e7imde b\u00fcy\u00fcyerek, beynin geri kalan b\u00f6l\u00fcm\u00fc \u00fcst\u00fcne yerle\u015fmi\u015ftir. Beyin k\u0131vr\u0131mlar\u0131n\u0131n azl\u0131\u011f\u0131 ya da \u00e7oklu\u011fu, bir \u00f6l\u00e7\u00fcde canl\u0131n\u0131n v\u00fccut b\u00fcy\u00fckl\u00fc\u011f\u00fcne ba\u011fl\u0131d\u0131r. Kar\u0131nca yiyen ve marmoset gibi k\u00fc\u00e7\u00fck yap\u0131l\u0131 memelilerin beyinleri genellikle d\u00fcz denecek kadar az k\u0131vr\u0131ml\u0131, balina, fil ve yunus gibi b\u00fcy\u00fck memelilerin beyinleri ise \u00e7ok k\u0131vr\u0131ml\u0131d\u0131r.
\n Bu b\u00fcy\u00fck memelilerden baz\u0131lar\u0131nda, \u00f6rne\u011fin balina ve yunusta beyin kabu\u011fundaki bozmaddenin \u00e7ok ince olmas\u0131na kar\u015f\u0131l\u0131k, insanda ve insans\u0131 maymunlarda bozmadde genellikle daha kal\u0131n ve \u00e7ok daha farkl\u0131la\u015fm\u0131\u015ft\u0131r.<\/p>\n
Beyin yar\u0131mk\u00fcreleri, \u00f6nden arkaya do\u011fru uzanan derin bir yar\u0131kla birbirinden ayr\u0131lm\u0131\u015ft\u0131r. Bu yar\u0131\u011f\u0131n taban\u0131nda, iki yar\u0131mk\u00fcre aras\u0131ndaki ileti\u015fim ba\u011flant\u0131s\u0131n\u0131 sa\u011flayan ve kat\u0131 madde, nas\u0131rs\u0131 madde, beyin dire\u011fi gibi adlarla an\u0131lan kal\u0131n bir sinir lifi demeti (corpus callosun\u0131) bulunur. Sinir lifleri so\u011fanilikte ya da ender olarak. Omurilikte \u00e7aprazlanarak y\u00f6n de\u011fi\u015ftirdikleri i\u00e7in, beynin sol yar\u0131mk\u00fcresi v\u00fccudun sa\u011f yan\u0131n\u0131, sa\u011f yar\u0131mk\u00fcresi ise sol yan\u0131n\u0131 denetler. Her ne kadar sa\u011f ve sol yar\u0131mk\u00fcre bir\u00e7ok bak\u0131mdan birbirinin ayna g\u00f6r\u00fcnt\u00fcs\u00fc bi\u00e7imindeyse de, aralar\u0131nda \u00f6nemli i\u015flevsel farkl\u0131l\u0131klar vard\u0131r. \u00d6rne\u011fin bir\u00e7ok ki\u015fide konu\u015fmay\u0131 denetleyen b\u00f6lgeler sol yar\u0131mk\u00fcrede, mekan alg\u0131s\u0131n\u0131 denetleyen b\u00f6lgeler ise sa\u011f yar\u0131mk\u00fcrede bulunur.
\n Orta oluk (Rolando yar\u0131\u011f\u0131) ve yanal oluk (Sylvius yan\u0131\u011f\u0131) denen iki derin yar\u0131k, beyin yar\u0131mk\u00fcrelerinden her birini al\u0131n yan kafa,\u015fakak ve art kafa loplar\u0131 olarak bilinen d\u00f6rt par\u00e7aya b\u00f6ler. Orta oluk, beyin kabu\u011fununhareket sinirlerinin u\u00e7lar\u0131n\u0131 alan b\u00f6lgesi (yar\u0131\u011f\u0131n \u00f6n\u00fcndeki b\u00f6lge) ile duyu sinirlerinin u\u00e7lar\u0131n\u0131 alan b\u00f6lgesini de (yar\u0131\u011f\u0131n arkas\u0131ndaki b\u00f6lge) birbirinden ay\u0131r\u0131r (bak. beyin oluklar\u0131
\n \u0130nsan beyninin a\u011f\u0131rl\u0131\u011f\u0131, ya\u015fa, boya, v\u00fccut a\u011f\u0131rl\u0131\u011f\u0131na, cinsiyete ve \u0131rka ba\u011fl\u0131 olarak de\u011fi\u015fir. Beyin, erkeklerde ortalama a\u011f\u0131rl\u0131\u011f\u0131 olan 1.400 gr\u2019a 20 ya\u015f dolaylar\u0131nda, kad\u0131nlarda ise ortalama a\u011f\u0131rl\u0131\u011f\u0131 olan 1.260 gr\u2019a biraz daha erken ya\u015fta ula\u015f\u0131r. Bu ya\u015ftan sonra her iki cinste de beynin ortalama a\u011f\u0131rl\u0131\u011f\u0131 her y\u0131l bir gram kadar eksilerek, 75 ya\u015flar\u0131nda, olgunluk d\u00f6neminde eri\u015fti\u011fi tepe de\u011ferinin onda biri kadar azal\u0131r. 20-70 ya\u015flar\u0131 aras\u0131nda, insan beyninde her g\u00fcn yakla\u015f\u0131k 50 bin sinir h\u00fccresinin (n\u00f6ron) g\u00f6rev yapamaz duruma geldi\u011fi ya da yok oldu\u011fu tahmin edilmektedir.<\/p>\n
Beyin kabu\u011fu, beyin korteksi olarak da bilinir, beyin yar\u0131mk\u00fcrelerinin, sinir sisteminin bozmaddesinden olu\u015fan ve istemli hareketlerin denetlenmesinden, duyular\u0131n birle\u015ftirilip y\u00f6nlendirilmesinden, y\u00fcksek d\u00fczeydeki zihinsel ve duygusal i\u015flevlerin d\u00fczenlenmesinden sorumlu olan en d\u0131\u015f katman\u0131.
\n Beyin kabu\u011funu olu\u015fturan h\u00fccreler, kesin s\u0131n\u0131rlarla birbirinden ayr\u0131lmam\u0131\u015f alt\u0131 kat-manda toplan\u0131r:
\n 1)Molek\u00fcll\u00fc katman,
\n 2) tanecikli d\u0131\u015f katman,
\n 3) piramidimsi d\u0131\u015f katman,
\n 4) tanecikli i\u00e7 katman,
\n 5) piramidimsi i\u00e7 katman,
\n 6) i\u011fsi h\u00fccreler katman\u0131.
\n Her iki yar\u0131mk\u00fcreyi \u00f6rten beyin kabu\u011fu, getirici sinir liflerinin da\u011f\u0131l\u0131m\u0131na ya da daha derindeki sinir merkezleriyle ba\u011flant\u0131l\u0131 olan g\u00f6t\u00fcr\u00fcc\u00fc liflerin k\u00f6kenine g\u00f6re de birka\u00e7 b\u00f6l\u00fcme ayr\u0131l\u0131r. Bu ayr\u0131ma g\u00f6re, kabu\u011fun en \u00f6nemli i\u015flevsel b\u00f6l\u00fcmleri birincil hareket alan\u0131, birincil duyul alan\u0131, birincil g\u00f6rme alan\u0131, birincil i\u015fitme alan\u0131 ve birle\u015ftirme alanlar\u0131d\u0131r.
\n -Birincil hareket alan\u0131 beynin \u00f6n b\u00f6l\u00fcm\u00fcnde (al\u0131n lobu), orta olu\u011fun \u00f6n duvar\u0131nda bulunur. V\u00fccudun kar\u015f\u0131 yan\u0131ndaki iskelet kaslar\u0131 buradan y\u00f6netilir.
\n -Birincil duyu alan\u0131 beynin yan kafa b\u00f6l\u00fcm\u00fcnde yer al\u0131r ve deriden, kaslardan, eklemlerden, kas kiri\u015flerinden gelen duyular talamus arac\u0131l\u0131\u011f\u0131yla bu alana ula\u015f\u0131r. Burada da, hareket alan\u0131ndaki gibi, v\u00fccudun \u00e7e\u015fitli b\u00f6lgelerine kar\u015f\u0131l\u0131k d\u00fc\u015fen \u00f6zel b\u00f6lgeler vard\u0131r. Duyu alan\u0131n\u0131n y\u0131k\u0131m\u0131, duyular\u0131n alg\u0131lanmas\u0131n\u0131 azalt\u0131r ama t\u00fcm\u00fcyle yok etmez; \u00e7\u00fcnk\u00fc, a\u011fr\u0131 gibi baz\u0131 \u00f6nemli duyumlar talamusta bilin\u00e7 d\u00fczeyine ula\u015f\u0131r.
\n -Birincil g\u00f6rme alan\u0131, beyin kabu\u011funun art kafa b\u00f6l\u00fcm\u00fcndeki mahmuzumsu yar\u0131kta bulunur; bu alan\u0131n y\u0131k\u0131m\u0131 g\u00f6rme bozukluklar\u0131na, hatta yitimine yol a\u00e7ar.
\n -Birincil i\u015fitme alan\u0131 \u015fakak b\u00f6l\u00fcm\u00fcnde, yanal beyin yar\u0131\u011f\u0131n\u0131n taban\u0131nda bulunur ve y\u0131k\u0131m\u0131 orta derecede sa\u011f\u0131rl\u0131kla sonu\u00e7lan\u0131r.
\n -\u00c7e\u015fitli hareket ve duyu alanlar\u0131yla ba\u011flant\u0131l\u0131 olan birle\u015ftirme alanlar\u0131, \u00fcst\u00fcn yap\u0131l\u0131 omurgal\u0131larda beyin kabu\u011funun \u00e7ok b\u00fcy\u00fck bir b\u00f6l\u00fcm\u00fcn\u00fc\u2019 kaplar. Birincil duyu alanlar\u0131n\u0131n yak\u0131n\u0131ndaki birle\u015ftirme alanlar\u0131n\u0131n g\u00f6revi, duyulardan gelen uyar\u0131lar\u0131 g\u00f6r\u00fcnt\u00fclemek ve anlamland\u0131rmakt\u0131r. Al\u0131nan uyar\u0131lar \u00f6nceden ya\u015fanm\u0131\u015f deneyleri ve an\u0131lan \u00e7a\u011fr\u0131\u015ft\u0131rd\u0131\u011f\u0131nda, uyar\u0131lan veren nesne ya da olgu tan\u0131n\u0131r. Karma\u015f\u0131k istemli hareketlerin yap\u0131labilmesi i\u00e7in, \u00f6nce hareket plan\u0131n\u0131n tasarlanmas\u0131, sonra bu plan\u0131n birle\u015ftirici sinir lifleriyle hareket alanlar\u0131na aktar\u0131lmas\u0131 gerekir. Konu\u015fma i\u015flevinde de karma\u015f\u0131k hareket ve duyu birle\u015ftirme mekanizmalar\u0131 s\u00f6z konusudur.<\/p>\n
Beyin oluklar\u0131, beyin yar\u0131klar\u0131 olarak da bilinir, beyin yar\u0131mk\u00fcrelerinin d\u0131\u015f y\u00fczeyinde, beyin loplar\u0131 denen \u00e7e\u015fitli anatomik b\u00f6lgeleri birbirinden ay\u0131ran derin yar\u0131klard\u0131r. Bu oluklar, insan beyninin en i\u015flevsel b\u00f6l\u00fcm\u00fc olan beyin kabu\u011funun alan\u0131n\u0131 art\u0131racak bi\u00e7imde, beyin y\u00fczeyinin katlan\u0131p k\u0131vr\u0131mla\u015fmas\u0131ndan ileri gelir. Beyin oluklar\u0131n\u0131n en belirginleri \u015funlard\u0131r: Al\u0131n ve \u015fakak loplar\u0131 aras\u0131ndaki yanal oluk ya da Sylvius yar\u0131\u011f\u0131; al\u0131n ve yan kafa loplan aras\u0131nda, birincil hareket ve duyu alanlar\u0131n\u0131 birbirinden ay\u0131ran orta oluk ya da kolando yar\u0131\u011f\u0131; beyin kabu\u011funun g\u00f6rme alan\u0131n\u0131 bar\u0131nd\u0131ran art kafa lobundaki mahmuzumsu yar\u0131k; yan-kafa ve artkafa loplar\u0131n\u0131 ay\u0131ran yan kafa art kafa olu\u011fu; beyin yar\u0131mk\u00fcrelerini beyincikten ay\u0131ran enine oluk ve yaln\u0131zca nas\u0131rs\u0131 (kat\u0131) madde arac\u0131l\u0131\u011f\u0131yla aralar\u0131nda ba\u011flant\u0131 kalacak bi\u00e7imde, iki yar\u0131mk\u00fcreyi hemen hemen b\u00fct\u00fcn\u00fcyle ay\u0131ran boylamas\u0131na oluk.<\/p>\n
Beyin-omurilik s\u0131v\u0131s\u0131, beyin kar\u0131nc\u0131klar\u0131n\u0131 ve omurilik i\u00e7 kanal\u0131n\u0131 dolduran, ayr\u0131ca bu olu\u015fumlar\u0131n \u00e7evresini sararak s\u00fcrt\u00fcnmeleri engelleyen ve darbelerden koruyan duru, renksiz s\u0131v\u0131.
\n Beyin omurilik s\u0131v\u0131s\u0131 daha \u00e7ok beyin kar\u0131nc\u0131klar\u0131nda olu\u015fur, beyin sap\u0131ndaki kanaldan a\u015fa\u011f\u0131ya do\u011fru akar ve \u00e7evredeki doku bo\u015fluklar\u0131 taraf\u0131ndan emilerek merkez sinir sisteminden ayr\u0131l\u0131r. Normal bir yeti\u015fkinin v\u00fccudunda 100-150 mI kadar beyin-omurilik s\u0131v\u0131s\u0131 vard\u0131r.
\n Beyin omurilik s\u0131v\u0131s\u0131 daha \u00e7ok mekanik i\u015flevler \u00fcstlenir: Beynin a\u011f\u0131rl\u0131\u011f\u0131n\u0131 ta\u015f\u0131r; beyin ve omurili\u011fi \u00e7evreleyen zarlar ile kafatas\u0131 kemiklerinin i\u00e7 y\u00fczeyini d\u00f6\u015feyen zarlar aras\u0131ndaki s\u00fcrt\u00fcnmeleri azaltmak i\u00e7in y\u00fczeylere kayganl\u0131k kazand\u0131r\u0131r; ba\u015fa sert bir cisim \u00e7arpt\u0131\u011f\u0131nda, darbenin etkisini da\u011f\u0131tan bir tampon i\u015flevi g\u00f6r\u00fcr. Ayr\u0131ca, sinir sistemi i\u00e7inde \u00e7e\u015fitli maddelerin ta\u015f\u0131nmas\u0131, \u00f6rne\u011fin metabolizma art\u0131klar\u0131n\u0131n, antikorlar\u0131n, hastal\u0131k \u00fcr\u00fcn\u00fc olan \u00e7e\u015fitli maddelerin beyin ve omurilikten kan dola\u015f\u0131m\u0131na aktar\u0131lmas\u0131, baz\u0131 ila\u00e7lar\u0131n sinir sistemi dokular\u0131na ula\u015ft\u0131r\u0131lmas\u0131 da beyin omurilik s\u0131v\u0131s\u0131 arac\u0131l\u0131\u011f\u0131yla olur.<\/p>\n
Beyin sap\u0131, t\u00fcmbeyn\u0131n (ensefal), beyin yar\u0131mk\u00fcrelerinin alt\u0131nda kalan ve orta beyni, Varol k\u00f6pr\u00fcs\u00fcn\u00fc ve so\u011fanili\u011fi i\u00e7eren b\u00f6l\u00fcm\u00fc. Anatomi incelemelerinde\u2019 \u00e7o\u011fu kez, talamus ve hipotalamusu i\u00e7eren ara beyin ile gene art kafa \u00e7ukurunda, beyin sap\u0131yla ayn\u0131 kesimde bulunan beyincik de bu b\u00f6l\u00fcmden say\u0131l\u0131r. Ara beyin (diensefal) ve orta beyin (mezensefal) b\u00f6lgesine \u00fcst beyin sap\u0131, Varol k\u00f6pr\u00fcs\u00fc ile so\u011fanili\u011fe alt beyin sap\u0131 denir. Beyin sap\u0131n\u0131n ayr\u0131 bir birim olarak kabul edilmesinin temel nedeni, refleks hareketlerin, duyu ve hareket iletisinin denetlenmesinde, v\u00fccudun i\u00e7 ortam\u0131n\u0131n d\u00fczenlenmesinde ve sinir sisteminin geri kalan b\u00f6l\u00fcm\u00fcn\u00fcn e\u015fg\u00fcd\u00fcm\u00fcnde \u00e7ok \u00f6zel i\u015flevler \u00fcstlenmi\u015f olmas\u0131d\u0131r. Beyin yar\u0131mk\u00fcreleri ile omurilik aras\u0131nda yer alan ve beynin bu farkl\u0131la\u015fm\u0131\u015f b\u00f6lgeleriyle ba\u011flant\u0131s\u0131 olan beyin sap\u0131, bu yap\u0131lardan her ikisiyle de baz\u0131 benzerlikler g\u00f6sterir. Beyin sap\u0131, giren sinirler arac\u0131l\u0131\u011f\u0131yla duyusal izlenimlerin al\u0131n\u0131p biriktirilmesinden sorumlu oldu\u011fu gibi, deri ve kaslara giden hareket sinirlerinin, ayr\u0131ca g\u00f6z, kulak, burun gibi duyu organlar\u0131na giden kafatas\u0131 sinirlerinin b\u00fcy\u00fck b\u00f6l\u00fcm\u00fc de beyin sap\u0131ndan \u00e7\u0131kar.<\/p>\n
Beyin yar\u0131mk\u00fcreleri, kafatas\u0131n\u0131n \u00fcst kesiminde beynin en geni\u015f b\u00f6l\u00fcm\u00fcn\u00fc olu\u015fturan, boylamas\u0131na derin bir yar\u0131kla iki par\u00e7aya ayr\u0131lm\u0131\u015f, \u00e7ok k\u0131vr\u0131ml\u0131 sinir dokusu k\u00fctleleri. Sa\u011f ve sol yar\u0131mk\u00fcreler aras\u0131ndaki tek ba\u011flant\u0131, altta, yar\u0131\u011f\u0131n taban\u0131nda uzanan ve nas\u0131rs\u0131 ya da kat\u0131 madde (corpus callosum) denen geni\u015f bir sinir demetidir. Yar\u0131mk\u00fcrelerin en d\u0131\u015f katman\u0131 olan beyin kabu\u011fu ya da korteksi, daha \u00e7ok sinir h\u00fccrelerini ve destek h\u00fccreleri i\u00e7eren bozmaddeden, i\u00e7 katmanlar\u0131 ise sinir h\u00fccrelerinin uzant\u0131lar\u0131 olan aksonlar\u0131 ya da sinir liflerini i\u00e7eren akmaddeden ve bazal gangliyonlardan yap\u0131lm\u0131\u015ft\u0131r.
\n En \u00fcst d\u00fczeyde zihinsel ve duygusal i\u015flevlerden sorumlu olan beyin yar\u0131mk\u00fcrelerinin en ilgin\u00e7 \u00f6zelliklerinden biri, her yar\u0131mk\u00fcrenin, beyin kabu\u011funca y\u00f6netilen bu i\u015flevleri, \u00f6b\u00fcr yar\u0131mk\u00fcrenin etkisini bast\u0131rarak denetim alt\u0131na alma e\u011filimidir.
\n Bu bask\u0131nl\u0131k \u00f6zellikle konu\u015fma alan\u0131nda kendini belli eder; sa\u011f elini kullanan ki\u015filerde konu\u015fma etkinli\u011fi sol yar\u0131mk\u00fcrenin denetimi alt\u0131ndad\u0131r.
\n Bask\u0131n ve bask\u0131n olmayan terimleri asl\u0131nda biraz yan\u0131lt\u0131c\u0131d\u0131r; bir anlamda, insanlar\u0131n iki beyinli oldu\u011fu s\u00f6ylenebilir: Bask\u0131n denen yar\u0131mk\u00fcre s\u00f6zl\u00fc anlat\u0131mda \u00f6n plana \u00e7\u0131karken, \u00f6b\u00fcr yar\u0131mk\u00fcre de y\u00fczlerin an\u0131msanmas\u0131 gibi karma\u015f\u0131k alg\u0131lama olaylar\u0131nda bask\u0131nl\u0131\u011f\u0131n\u0131 g\u00f6sterir.<\/p>\n
Beyin zarlar\u0131, BEY\u0130N OMUR\u0130L\u0130K ( ZARLARI. MENENJ ya da MENINKS olarak da bilinir, beyni ve omurili\u011fi saran \u00fc\u00e7 zars\u0131 k\u0131l\u0131f: \u0130nce zar (pia mater), \u00f6r\u00fcmceksi zar (arach\u0131\u0131oidea ya da araknoit) ve sert zar (dura mater). Beyin kar\u0131nc\u0131klar\u0131n\u0131 ve \u00f6r\u00fcmceksi zar ile ince zar aras\u0131ndaki bo\u015flu\u011fu beyin-omurilik s\u0131v\u0131s\u0131 doldurur. Beyin zarlar\u0131n\u0131n ve beyin-omurilik s\u0131v\u0131s\u0131n\u0131n temel i\u015flevi merkez sinir sistemini korunakt\u0131r.
\n \u0130nce zar. \u0130nce zar, do\u011frudan do\u011fruya beyin ve omurilik y\u00fczeyine de\u011fen ve bu yap\u0131lara s\u0131k\u0131ca yap\u0131\u015fm\u0131\u015f, olan i\u00e7 \u00f6rt\u00fcd\u00fcr. Lifli dokudan yap\u0131lm\u0131\u015f, \u00e7ok ince bir zar olan bu \u00f6rt\u00fcn\u00fcn d\u0131\u015f y\u00fczeyi, s\u0131v\u0131lar\u0131 ge\u00e7irmedi\u011fi san\u0131lan yass\u0131 ve \u00e7okgen h\u00fccrelerden olu\u015fmu\u015f bir katmanla kapl\u0131d\u0131r. Beyne ve omurili\u011fe giden kan damarlar\u0131 ince zar\u0131 delerek ge\u00e7er. \u0130nce zar bu damarlarla birlikte beynin derinliklerine do\u011fru ilerler ve kan damarlar\u0131yla aras\u0131nda k\u00fc\u00e7\u00fck bir bo\u015fluk b\u0131rakarak. sinir dokusuna s\u0131k\u0131ca yap\u0131\u015f\u0131r.
\n \u00d6r\u00fcmceksi zar. \u0130nce zar\u0131n \u00fcst\u00fcnde yer alan bu ikinci zar ile ince zar aras\u0131nda, \u00f6r\u00fcmceksi zar alt\u0131 aral\u0131k denen bir bo\u015fluk bulunur. Son derece ince, saydam ve kolayca \u00f6rselenebilen bir doku olan \u00f6r\u00fcmceksi zar da lifli dokudan yap\u0131lm\u0131\u015ft\u0131r ve ince zar gibi, b\u00fcy\u00fck olas\u0131l\u0131kla s\u0131v\u0131lar\u0131 ge\u00e7irmeyen yass\u0131 ve \u00e7ok-gen h\u00fccrelerden olu\u015fmu\u015f bir katmanla kapl\u0131d\u0131r. Yaln\u0131z, \u00f6r\u00fcmceksi zar, ince zardan farkl\u0131 olarak, beyin y\u00fczeyindeki b\u00fct\u00fcn girinti ve \u00e7\u0131k\u0131nt\u0131lar\u0131 izlemez; bu \u00f6zelli\u011fiyle, sinir sisteminin y\u00fczeyi ile duvarlar\u0131 aras\u0131nda bazen dar, bazen geni\u015f bo\u015fluklar bulunan bol bir torba gibi d\u00fc\u015f\u00fcn\u00fclebilir.
\n Sert zar. \u00dc\u00e7 beyin zar\u0131n\u0131n en d\u0131\u015fta bulunan\u0131, kal\u0131n, sa\u011flam ve yo\u011fun lifli dokudan olu\u015fan sert zard\u0131r. Bu zar\u0131n i\u00e7 y\u00fczeyi, ince zar\u0131n ve \u00f6r\u00fcmceksi zar\u0131n y\u00fczeyindekilere benzeyen yass\u0131, \u00e7okgen h\u00fccrelerle kapl\u0131d\u0131r. \u00d6b\u00fcr iki zardan \u00e7ok daha karma\u015f\u0131k bir d\u00fczeni olan sert zar, basit bir tan\u0131mla, \u00f6r\u00fcmceksi zar\u0131 saran ve \u00e7ok \u00e7e\u015fitli i\u015flevleri y\u00fcklenebilecek bi\u00e7imde de\u011fi\u015fikli\u011fe u\u011fram\u0131\u015f olan bir kesedir.
\n Sert zar\u0131n kafatas\u0131 i\u00e7inde kalan b\u00f6l\u00fcm\u00fc, beyin dokular\u0131ndan ald\u0131\u011f\u0131 kan\u0131 kalbe ta\u015f\u0131yan b\u00fcy\u00fck toplardamar kanallar\u0131n\u0131 (sin\u00fcsleri) \u00e7evreler ve destekler. Ayr\u0131ca, ara b\u00f6lme denen \u00e7ok say\u0131da \u00e7\u0131k\u0131nt\u0131yla beyne de destek olur.<\/p>\n","protected":false},"excerpt":{"rendered":"
Beyin, omurgal\u0131larda, kafatas\u0131 bo\u015flu\u011funun i\u00e7inde yer alan ve merkez sinir sisteminin \u00f6n b\u00f6l\u00fcm\u00fcn\u00fc olu\u015fturan, yo\u011funla\u015fm\u0131\u015f sinir dokusu. Duyular arac\u0131l\u0131\u011f\u0131yla al\u0131nan verilen birle\u015ftirip b\u00fct\u00fcnleyerek, bu uyar\u0131lara yan\u0131t niteli\u011findeki hareketleri y\u00f6neten, bu nedenle temel i\u00e7g\u00fcd\u00fcsel etkinliklerde \u00e7ok \u00f6nemli bir rol oynayan beyin, \u00fcst\u00fcn yap\u0131l\u0131 omurgal\u0131larda ayn\u0131 zamanda \u00f6\u011frenme merkezidir. Omurgas\u0131zlar\u0131n beyni, bir dizi sinir kordonunun \u00f6n ucunda …<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1407,1403],"tags":[9308,2510,2518,5700,6572,3378,2413,2429,2403,3382],"class_list":["post-4166","post","type-post","status-publish","format-standard","hentry","category-fen-ve-teknoloji-odevleri","category-odevler","tag-arka-beyin","tag-beyin","tag-beyin-omurilik-sivisi","tag-beyin-sapi","tag-corpus-callosum","tag-embriyo","tag-hipotalamus","tag-hormon","tag-noron","tag-omurgalilar"],"_links":{"self":[{"href":"https:\/\/www.islamidavet.com\/kutuphane\/wp-json\/wp\/v2\/posts\/4166","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.islamidavet.com\/kutuphane\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.islamidavet.com\/kutuphane\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.islamidavet.com\/kutuphane\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.islamidavet.com\/kutuphane\/wp-json\/wp\/v2\/comments?post=4166"}],"version-history":[{"count":0,"href":"https:\/\/www.islamidavet.com\/kutuphane\/wp-json\/wp\/v2\/posts\/4166\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.islamidavet.com\/kutuphane\/wp-json\/wp\/v2\/media?parent=4166"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.islamidavet.com\/kutuphane\/wp-json\/wp\/v2\/categories?post=4166"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.islamidavet.com\/kutuphane\/wp-json\/wp\/v2\/tags?post=4166"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}