Kapangidwe ndi Ntchito ya Maselo a Schwann
Maselo a Schwann ndi mtundu wa maselo a glial (selo lothandizira) omwe amapezeka mu dongosolo la mitsempha ya m'mphepete mwa mitsempha (PNS). Ntchito yawo yayikulu ndi yofunika kwambiri chifukwa ndi omwe amachititsa kupanga myelin, kuteteza axon, komanso kuthandiza kukonza mitsempha pambuyo povulala. Popanda maselo a Schwann, mitsempha ya mitsempha singathe kuyenda bwino komanso mwachangu monga momwe thupi limafunikira kuti ligwirizane ndi kayendedwe, kumva, komanso ntchito zosiyanasiyana za ziwalo. Nkhaniyi ikufotokoza kapangidwe ka maselo a Schwann, momwe amagwirira ntchito, komanso ntchito zofunika kwambiri zomwe zimawapangitsa kukhala ofunikira pa thanzi la mitsempha.
Tanthauzo ndi malo a maselo a Schwann mu dongosolo lamanjenje
Mu dongosolo lamanjenje, maselo a glial amagwira ntchito ngati "gulu lothandizira" ma neuron. Mu dongosolo lamanjenje lapakati (CNS), monga ubongo ndi msana, myelin imapangidwa ndi oligodendrocytes. Pakadali pano, mu dongosolo lamanjenje la m'mphepete mwa mitsempha, udindo uwu umagwera m'maselo a Schwann. Maselo a Schwann amalumikizana ndi ma neuronal axons ndipo, kudzera mu njira zinazake, amawaphimba, ndikupanga myelin kapena chidendene china choteteza, kutengera mtundu wa axon yomwe amagwira ntchito.
Maselo a Schwann amapezeka pafupifupi m'mitsempha yonse ya m'mphepete mwa thupi, kuphatikizapo mitsempha ya kumva (yonyamula chidziwitso kuchokera ku ma receptors kupita ku ubongo), mitsempha yoyendetsa (yonyamula malamulo kuchokera ku ubongo kupita ku minofu), ndi mitsempha yodziyimira yokha (yolamulira ziwalo zamkati popanda kuzindikira).
Kapangidwe koyambira ka maselo a Schwann
Kawirikawiri, maselo a Schwann ali ndi kapangidwe kake komwe kamasinthidwa kuti kagwirizane ndi ntchito yawo monga chophimba ndi chithandizo cha ma axon. Zina mwa zigawo zake zofunika ndi izi:
1. Thupi la selo ndi nucleus ya selo
Maselo a Schwann ali ndi ma nuclei omwe nthawi zambiri amakhala m'mphepete mwa selo, makamaka pamene selo likupanga myelin. Malo "ozungulira" a nyukiliyasiyi akugwirizana ndi ma coil ambiri opangira myelin m'malo ena.
2. Plasma nembanemba yomwe imazungulira axon
Khalidwe lalikulu la maselo a Schwann ndi luso lawo lozungulira ma axon. Nembanemba yawo ya plasma imazungulira mobwerezabwereza axon kuti ipange gawo lokhala ndi zigawo zambiri komanso lolemera mafuta. Gawoli limatchedwa myelin sheath, lomwe limagwira ntchito ngati chotetezera magetsi.
3. Chigoba cha mafupa ndi ziwalo zamkati
Monga maselo ena, maselo a Schwann ali ndi cytoplasm yokhala ndi organelles (mitochondria, endoplasmic reticulum, Golgi apparatus) kuti apange mphamvu ndikuyendetsa kupanga mapuloteni. Mapuloteni ena ndi ofunikira kuti myelin ikhale yolimba komanso kuti azitha kulumikizana ndi ma axon.
4. Basal lamina (basal lamina)
Chinthu chimodzi chofunikira kwambiri pa maselo a Schwann ndi kukhalapo kwa basal lamina yozungulira maselo. Gawoli limagwira ntchito yothandizira kapangidwe kake, limapereka kulumikizana kwa maselo, ndipo ndilofunika kwambiri pakubwezeretsa mitsempha pambuyo povulala. Basal lamina ikhoza kugwira ntchito ngati "njanji" kapena njira, kuthandiza axon kukulanso.
Mitundu ya maselo a Schwann kutengera ntchito yake
Maselo a Schwann nthawi zambiri samapanga myelin. Pali magulu awiri akuluakulu:
1. Maselo a Schwann Opanga Myelo (maselo a Schwann Opanga Myelo)
Myelin ya selo limodzi la Schwann nthawi zambiri imazungulira gawo limodzi la axon. Kugawikana kumeneku kumapanga mipata yaying'ono pakati pa zipolopolo za myelin zotchedwa nodes za Ranvier. Ma nodes a Ranvier ndi ofunikira kuti ma impulses afalikire mwachangu kudzera mu saltatory conduction (ma impulses "akudumpha" kuchokera ku node imodzi kupita ku ina).
2. Maselo a Schwann osapanga myelin (maselo a Schwann osapanga myelin)
Mu ma axon ang'onoang'ono a m'mimba mwake, maselo a Schwann samapanga myelin yokhuthala, koma m'malo mwake amasonkhanitsa ma axon angapo pamodzi mu "ma bundle" otchedwa Remak bundles. Ngakhale kuti sanalowe m'ma myelin, maselo a Schwann amaperekabe chithandizo ndi chitetezo cha kagayidwe kachakudya.
Kapangidwe ka Myelin ndi ma node a Ranvier
Chigoba cha myelin chimapangidwa ndi membrane wolemera mafuta ambiri, zomwe zimapangitsa kuti chikhale choteteza. Chigobachi chimachepetsa kutuluka kwa magetsi kuchokera ku axon ndikufulumizitsa kufalikira kwa mphamvu zogwira ntchito. Mu mitsempha ya myelinated, ma impulses samayenda mosalekeza, koma m'malo mwake "amalumphira" pakati pa mfundo za Ranvier. Kutulutsa mchere kumeneku kumathamanga kwambiri komanso kumawononga mphamvu kuposa kuyenda mu axon membrane yonse.
Kuphatikiza apo, pali malo apadera pa axon yomwe ili pafupi ndi node, monga paranode ndi juxtaparanode, zomwe zili ndi mapuloteni ambiri a ion channel ndi mapuloteni omatira. Maselo a Schwann amachita gawo lofunikira pakusunga dongosololi kuti asunge zizindikiro zokhazikika za mitsempha.
Ntchito yaikulu ya maselo a Schwann
1. Amapanga myelin ndikufulumizitsa kutumiza kwa impulse
Ntchito yake yodziwika bwino ndi kupanga ma myelin sheaths pa mitsempha ya m'mphepete mwa mitsempha. Myelin imawonjezera kwambiri liwiro la kutumiza kwa impulse. Izi zimathandiza kuti kayendedwe ka thupi kagwire ntchito mwachangu komanso molondola (monga kubweza dzanja likakhudzidwa ndi kutentha) komanso kusinthidwa kwa masensa (kumva kukhudza pang'ono).
2. Kudzipatula ndi kuteteza ma axon
Myelin imagwira ntchito ngati chotetezera magetsi, pomwe maselo a Schwann nthawi zambiri amaperekanso chitetezo chakuthupi ku ma axon. Chitetezochi chimapangitsa ma axon kukhala olimba kwambiri ku zovuta zomwe zimachitika m'malo ozungulira minofu.
3. Chithandizo cha kagayidwe kachakudya ka ma neuron
Ma neuron amafuna mphamvu zambiri, ndipo ma axon amatha kukhala aatali kwambiri. Maselo a Schwann amathandiza kuonetsetsa kuti ma axon amalandira chithandizo cha kagayidwe kachakudya kudzera mu kusinthana kwa michere ndi ma signal a mamolekyu. Udindo uwu ndi wofunikira kwambiri kuti ntchito ya axon ikhale yolimba kwa nthawi yayitali.
4. Kubwezeretsa mitsempha pambuyo povulala
Chimodzi mwa ubwino wa dongosolo la mitsempha ya m'mphepete mwa mitsempha kuposa dongosolo lapakati la mitsempha ndi mphamvu yake yabwino yokonzanso. Maselo a Schwann amachita gawo lofunika kwambiri pa njirayi kudzera m'magawo angapo:
– Kusanduka ndi kufalikira: pambuyo povulala, maselo a Schwann ozungulira malo owonongeka amasintha kukhala mawonekedwe othandizira kukonzanso, kenako amachulukana.
– Kuyeretsa zinyalala za myelin: Maselo a Schwann amagwira ntchito ndi macrophages kuyeretsa zinyalala za myelin zomwe zingalepheretse kubwezeretsedwa kwa maselo.
– Kupanga “Mizere ya Büngner”: Maselo a Schwann amakonza okha kuti apange njira yomwe imatsogolera kukula kwa ma axon kupita ku zolinga zawo.
– Kutulutsa zinthu zomwe zimayambitsa kukula kwa mitsempha: Maselo a Schwann amapanga mamolekyu monga ma neurotrophin ndi zinthu zina zomwe zimayambitsa kukula kwa axon.
Popanda thandizo la maselo a Schwann, kubwezeretsedwa kwa axon mu PNS kungakhale kochedwa kwambiri komanso kosalunjika kwambiri.
5. Amayang'anira kukula ndi kukhwima kwa mitsempha
Maselo a Schwann ndi ofunikira kuyambira pakukula kwa mwana wosabadwayo mpaka kukula. Amathandiza kukulitsa kulumikizana kwa mitsempha, kudziwa ma axon omwe adzalowetsedwa myelini, ndikusintha makulidwe a myelin malinga ndi kukula kwa axon. Ubale uwu ndi wosinthasintha: ma axon amatumiza zizindikiro ku maselo a Schwann, ndipo maselo a Schwann amapereka mayankho omwe amakhudza kukhazikika kwa axon ndi ntchito yake.
6. Udindo mu chitetezo chamthupi ndi kutupa komwe kumachitika m'deralo
Pazifukwa zina, maselo a Schwann amatha kukhala ndi gawo pa mayankho a chitetezo chamthupi cha m'deralo. Amatha kupanga mamolekyu odziwitsa omwe amasonkhanitsa maselo a chitetezo chamthupi kapena kusintha kutupa. Izi ndizofunikira pankhani ya kuvulala kwa mitsempha ndi matenda.
Kufunika kwachipatala: pamene maselo a Schwann afooka
Kuwonongeka kapena kusagwira bwino ntchito kwa maselo a Schwann kungayambitse matenda a mitsempha ya m'mitsempha. Mwachitsanzo:
– Guillain-Barré syndrome (GBS): vuto la autoimmune lomwe nthawi zambiri limaukira myelin mu PNS, zomwe zimapangitsa kuti minofu ifooke komanso kusokonezeka kwa malingaliro.
– Charcot–Marie–Tooth (CMT): gulu la matenda a majini omwe angakhudze kusokonekera kwa mapangidwe a myelin kapena ntchito ya maselo a Schwann, zomwe zimapangitsa kufooka kwa minofu yakutali ndi kusokonezeka kwa kayendedwe ka thupi.
– Neuroma ndi schwannoma: zotupa zochokera ku maselo a Schwann, nthawi zambiri zimakhala zopanda vuto koma zimatha kukakamiza mapangidwe a mitsempha ndikuyambitsa zizindikiro.
Kumvetsetsa maselo a Schwann ndikofunikira kwambiri pa kafukufuku wokhudza njira zochiritsira zobwezeretsa mitsempha, uinjiniya wa minofu, komanso kupanga mankhwala ochizira matenda ochotsa myelin.
Mapeto
Maselo a Schwann ndi ofunikira kwambiri mu dongosolo la mitsempha ya m'mphepete mwa thupi. Mwa kapangidwe kake, maselowa ali ndi luso lapadera lophimba ma axon, kupanga myelin, ndikupereka basal lamina, yomwe ndi yofunika kwambiri kuti munthu akhale wolimba komanso wosinthika. Mwa kugwira ntchito, maselo a Schwann amafulumizitsa kutumiza kwa impulse kudzera mu saltatory conduction, kuteteza ma axon, kuthandizira kagayidwe ka mitsempha ya m'mitsempha, kuwongolera kukula kwa mitsempha, komanso kuchita gawo lofunika kwambiri pakukonzanso mitsempha ya m'mphepete mwa thupi pambuyo povulala. Pomvetsetsa kapangidwe ndi ntchito ya maselo a Schwann, titha kumvetsetsa bwino momwe mitsempha imagwirira ntchito komanso momwe njira zamankhwala zingapangidwire kuti zithetse mavuto osiyanasiyana a mitsempha ya m'mphepete mwa thupi.
