Kasana sun bayyana ƙwaƙwalwar ɗan’adam a matsayin abin da ya fi komai wuyar fahimta (complex) a gabaɗaya faɗin duniya. Duk da cewa ana kwatanta ta da na’ura mai ƙwaƙwalwa, amma ta fi kowace kwamfiyuta da aka taɓa kirkira. Fahimtar yadda take aiki ya zama ɗaya daga cikin manyan wahalhalu da masana ilimin halitta (biologists) ke fuskanta. Amma duk da haka an samu cigaba.
Ƙwaƙwalwa tana ɗauke da kusan kimanin jijiyoyin cells guda miliyan ɗari, da kuma hanyoyi sama da mil 1000 na cerebral cortex. Wani ɓangare ne a cikin ƙwaƙwalwa.
Cerebral cortex ya kasu ga gida biyu kamar haka; akwai na baya, akwai na tsakiya. A cerebral cortex tunaninmu yake (consciousness).
Kowace jijiyar cell ta cikin cortex tana karbar aƙalla kusan mahaɗa 1000 to 10, 000 daga sauran jijiyoyin cells, hakan yana samar da haɗakar jijiyoyin cells masu matuƙar yawa. Dalilin wannan haɗakar ne ake kiran shi (neural network), abin da ke samar mana da tunani.
Duk da cewa a farkon ƙarni na 20, an ɗauka aikin da ƙwaƙwalwa take yi gabaɗaya sassanta ne yake ɗaukar nauyi (misali, motsin hannu, shan ruwa, numfashi, gabaɗaya ko’ina na ƙwaƙwalwa na ba da gudunmawa wajen aiwatarwa.
Asalin ƙwaƙwalwa
Za mu fi fahimtar ƙwaƙwalwa idan muka bincika asalin yadda take cikin kan simpler vertebrates (dabbobi masu ƙashin baya), da kuma mutane su kansu.
Ƙwaƙwalwar ta rabu kashi uku: the forebrain, midbrain, da hindbrain. Wadannan kashi-kashi na kwakwalwa ana ganin sa clearly tun dan mutum yana ciki a embryonic stage. Amma, labarin evolution (sauyawa) na vertebrates (dabbobi masu ƙashin baya) ya ƙunshi ƙaruwar girman ƙwaƙwalwa daidai da yanayin girman jiki. Ma’ana ƙwaƙwalwar vertebrates ta ƙara girma fiye da yadda take tun asali. Wannan ƙaruwar girman nata yawanci saboda ƙaruwar girman forebrain ne.
Forebrain ɗin tsuntsaye da mammals (dabbobi masu shayarwa. Mutane suna cikin waɗannan) ta fi ta amphibians da reptiles (irin su kwado, kada, miciji) girma. Sannan gaba ɗaya ma ƙwaƙwalwar mammals ta fi girma.
Forebrain ta mammal tana da dan tuntu wanda ya gangaro ta baya, ta saman midbrain da hindbrain, yadda da za a kalli ƙwaƙwalwa daga sama, to ba za a ga midbrain ba.
Idan muka koma ɓangaren mammals, primates (waɗannan su ne dabbobin da suka fi kowane dabba basira, kamar mutane, birrai da sauran su) sun fi ko wane dabba girman ƙwaƙwalwa daidai da yanayin jikinsu.
Amma a fahimta, girman ƙwaƙwalwar ba ya nufin quality. Ƙwaƙwalwar giwa ta linka ta mutum sau huɗu a nauyi, sannan ƙwaƙwalwar mutum da namiji ta fi ta mace girma. Wannan wata hujja ce da scientists a 19th century suka yi amfani da ita wajen nuna ƙwaƙwalwar maza ta fi ta mata (duk da cewa sun suna sane da jikin namiji ya fi na mace girma in general).
Ƙwaƙwalwar kifi, tana nuna gani (vision) na kifi a midbrain yake. Mutane kuma, duk da cewa idanu sun yi connecting da optic nerves daga midbrain, amma yawancin bayanan da idanu yake ɗaukowa kai tsaye suke wucewa forebrain, inda ita kuma take fassara su ta maida su gani (vision).
Hindbrain kuma ta mutane tana aiki ne kamar yadda hindbrain ta kifi take, sannan ta rabu zuwa: cerebellum, pons and medulla.
Da waɗannan ɓangarorin ya kamata mu fara karantar ƙwaƙwalwa da siffarta ta tare da aikinta.
Za mu san cerebellum, Pons, da Medulla saboda a cikin hindbrain suke.
Cerebellum (hindbrain)
A kanannade take sannan tana da bangaren waje wanda ake kira cortex (outer region). Misali, outside region na farce shi ne wanda ake kankarewa. Outside region na fata shi ne wanda gashi ya ke fitowa a kai kuma muke gani, inside ɗin kuma shi ne na can ciki). So cortex ta na ɗauke da nerve cells da cell bodies. (Nerve cells wasu ‘yan ƙananan jijiyoyi ne da suke karɓo saƙonni daga sassan jiki suke kawo wa ƙwaƙwalwa domin ta fassara su.
Misali, idan mutum ya taɓa hannun wani saitin inda aka taɓa akwai nerve cells, wasu suna kiran su neurons, wannan nerves cells ɗin za su ɗauki wannan sakon na taɓi da aka yi su kai wa ƙwaƙwalwa, ita kuma za ta fassara cewar an yi taɓin . Saboda gudun da suke irin na lantarki ne. So, basically mutane suna da lantarki su ma a jikinsu.
Ana kiran cerebellum da gyroscope of the body, saboda aikin ta shi ne kawo balance ga ɗan’adam. Misali, tsayuwa, za ta ba ki balance yadda za a tsayu da kafafuwa babu matsala. Ko zafin jiki, aikinta ne ta saita zafin jiki. Idan ya yi yawa, ta bayar da umarni a rage. Idan ya yi kaɗan ta bayar da umarni a ƙara. Da bugun zuciya, blood pressure da sauran su. Ita ce ta ke ji da duk wani mosti da za a yi wanda ganin damar mutum ne (voluntary movement). Misali, tafiya, zama, aiki, sa sauran su). Akwai motsin da babu control da shi, kamar bugun zuciya, blood circulation.
Mutanen da suka samu matsalar cerebellum, daga hatsari ko wani abin, da farko ba za su iya tafiya ba. Amma za su iya sake koyon tafiyar, sai dai za su yi ta wani iri saboda yanzu tafiyar ƙwaƙwalwa ba ta yin control ɗin ta automatically. Misali, dole yanzu mutum yana buƙatar ya maida hankali kan yadda zai yi tafiya. (Lokacin da ƙwaƙwalwa, kafin a samu matsalar kenan, ta ke control din tafiya automatically, mutum ba ya tsayawa yin tunanin yadda zai yi ta. Ya takunsa yake, ya zai yi, duka mutum babu ruwansa da wannan, kamar dai yadda muke yanzu, saboda ƙwaƙwalwar ta riga ta koya, yanzu ba sai mutum ya lura ba, automatically za ta dinga sarrafa tafiyar).
Mu dauki jarirai, lokacin da suke koyon tafiya, ba sa tunanin wani abu sai wannan tafiyar, amma a hankali cerebellum za ta koyi wannan, daga nan sai ya zama mutum ba sai ya tsaya tuna yadda zai yi ba, kawai sai dai ya yi.
Sauran kuma abubuwa kamar swimming, tuka keke, tukin mota, typing, yanayin tsayuwa (posture), magana, gudu, za su dawo mutum automatically yake ba tare da ya tsaya wani tunanin yadda ake ba da taimakon cerebellum.
Kamar yadda aka faɗa, haƙƙin cerebellum ne kula da duk wani motsin da mutum zai yi, wannan harda fine control of voluntary movement. Idan aka gwada ɗaukar fensir. Za a yi cikin sauki, ko da ace hankalin na kan abin da malami ke jawabi. Wannan saboda aikin cerebellum ne. Har yanzu ba a ƙirƙiri wata na’ura da za ta yi irin wannan abin ba, saboda ba a abu ne mai sauƙi ba. Shi ya sa da farko na ce miki ƙwaƙwalwa ta wuce ko wane irin nau’in kwamfiyuta.
Pons
Shi kuma wannan relay station ne kawai tsakanin cerebellum, spinal cord, da sauran bangaren ƙwaƙwalwa. Ma’ana shi ne yake karɓar saƙonni ya barbaza su inda ko wanne ya dace.
Medulla
Medulla na daya daga cikin bangaruruwan ƙwaƙwalwa da suka fi ko ina amfani. Idan da za a yanke saman ƙwaƙwalwa amma ba a taɓa medulla ba, numfashin mutum, bugawar zuciyarsa, za su zauna lafiya kalau. Amma fa idan ta yi dameji, aikin ya kwana. Ita ce take ɗauke da cardiovascular center (abin da ya shafi zuciya), wanda ha had6a da cardiac accelerator center da cardiac inhibitory center wanda su ke regulating na bugawar zuciya. Ita ce ta ke control ɗin blood pressure kamar yadda aka faɗa da vasoconstriction, da vasodilation. Medulla ita ce ke ɗauke da breathing center.
Motsin da mutum ba shi da control a kansu, aikin medulla ce, misali, atishawa, tari, haɗiya, amai. Amma waɗannan abubuwa suna faruwa ne by reflex.