Nerve fiber yog txheej txheem ntawm cov neuron uas tau them los ntawm glial sheath. Nws yog dab tsi? Nws ua haujlwm li cas? Nws npaj li cas? Koj yuav kawm txog qhov no los ntawm kab lus.
Kev faib tawm
Cov fibers ntawm lub paj hlwb muaj cov qauv sib txawv. Raws li lawv cov qauv, lawv tuaj yeem koom nrog ib qho ntawm ob hom. Yog li, unmyelinated thiab myelinated fibers yog cais. Cov qub muaj cov txheej txheem ntawm tes, uas nyob hauv nruab nrab ntawm cov qauv. Nws yog hu ua axon (axial cylinder). Cov txheej txheem no yog ib puag ncig los ntawm myelin sheath. Noj mus rau hauv tus account qhov xwm ntawm qhov kev siv ntawm lub functional load, tsim ntawm paj fibers ntawm ib hom los yog lwm yam tshwm sim. Cov qauv ntawm cov qauv ncaj qha nyob ntawm lub tuam tsev uas lawv nyob. Piv txwv li, myelinated paj fibers nyob rau hauv lub somatic ib feem ntawm lub paj hlwb, thiab unmyelinated sawv daws yuav nyob rau hauv lub vegetative ib feem. Tib lub sijhawm, nws yuav tsum tau hais tias cov txheej txheem ntawm kev tsim cov qauv no thiab lwm cov qauv ua raws li tus qauv zoo sib xws.
Yuav ua li cas lub paj hlwb nyias tshwm sim?
Cia peb xav txog cov txheej txheem kom ntxaws ntxiv. Nyob rau theem ntawm kev tsim cov qauv ntawm hom unmyelinated, lub axon tob rau hauv ib txoj hlua uas muaj cov lemmocytes,uas cytolemmas pib khoov thiab npog cov txheej txheem raws li lub hauv paus ntsiab lus ntawm lub clutch. Cov npoo nyob rau tib lub sij hawm kaw nyob rau hauv lub axon, thiab ib tug duplication ntawm lub cell membrane yog tsim, uas yog hu ua mesaxon. Lemmocytes nyob rau hauv cov zej zog tsim kev sib cuag yooj yim nrog kev pab los ntawm lawv cov cytolemmas. Myelin-dawb fibers, vim tsis muaj zog rwb thaiv tsev, muaj peev xwm xa cov hlab ntsha impulse ob leeg nyob rau hauv mesaxon cheeb tsam thiab nyob rau hauv lub cheeb tsam ntawm kev sib cuag ntawm lemmocytes. Vim li ntawd, nws txav ntawm ib lub fiber mus rau lwm qhov.
Tsim cov qauv tuab
Cov paj hlwb myelinated yog tuab dua li cov tsis muaj myelinated. Hais txog cov txheej txheem ntawm lub plhaub tsim, lawv yog tib yam. Txawm li cas los xij, kev loj hlob sai ntawm cov neurons hauv thaj av somatic, uas cuam tshuam nrog kev loj hlob ntawm tag nrho cov kab mob, pab txhawb rau elongation ntawm mesaxons. Tom qab ntawd, cov lemmocytes qhwv ib ncig ntawm axons ob peb zaug. Yog li ntawd, cov khaubncaws sab nraud povtseg ntawm ib hom concentric yog tsim, thiab cov nucleus nrog lub cytoplasm yog txav mus rau qhov kawg tig, uas yog lub plhaub sab nraud ntawm cov fiber ntau (neurilemma). Cov txheej sab hauv muaj mesaxon, entwined ob peb zaug, thiab hu ua myelin. Sij hawm dhau mus, tus naj npawb ntawm cov lem thiab qhov loj ntawm mesaxon maj mam nce. Qhov no yog vim qhov kev hla ntawm cov txheej txheem myelination thaum lub sij hawm loj hlob ntawm axons thiab lemmocytes. Txhua qhov tig tom ntej yog dav dua qhov dhau los. Qhov dav tshaj plaws yog ib qho uas muaj cov cytoplasm nrog ib tug lemmocyte nucleus. Tsis tas li ntawd, lub thickness ntawm myelin kuj txawv raws li qhov ntev ntawm fiber ntau. Nyob rau hauv cov chaw uas cov lemmocytes nyob rau hauv kev sib cuag nrog ib leeg, cov txheej yuav ploj mus. Hu rauTsuas yog cov txheej txheej sab nrauv nkag, uas suav nrog cytoplasm thiab nucleus. Cov chaw zoo li no tau tsim vim tsis muaj myelin hauv lawv, thinning ntawm fiber ntau thiab hu ua nodal intercepts.
Kev loj hlob ntawm cov qauv hauv CNS
Myelination nyob rau hauv lub kaw lus tau tshwm sim los ntawm cov txheej txheem ntawm oligodendrocytes qhwv ncig axons. Myelin muaj lub hauv paus lipid thiab, thaum cuam tshuam nrog oxides, tau txais cov xim tsaus. Cov khoom seem ntawm daim nyias nyias thiab nws qhov khoob nyob twj ywm. Xws li cov bands tshwm sim yog hu ua myelin notches. Lawv sib raug rau cov txheej tsis tseem ceeb hauv cytoplasm ntawm lemmocyte. Thiab nyob rau hauv lub cytoplasm ntawm axon muaj neurofibrils thiab mitochondria nyob longitudinally. Lawv tus lej loj tshaj plaws yog nyob ze rau qhov cuam tshuam thiab hauv qhov kawg ntawm cov khoom siv fibers. Lub axon cytolemma (axolemma) txhawb nqa kev ua haujlwm ntawm lub paj hlwb. Nws manifests nws tus kheej raws li ib tug nthwv dej ntawm nws depolarization. Nyob rau hauv rooj plaub thaum ib tug neurite raug nthuav tawm raws li lub tog raj kheej axial, nws tsis muaj granule ntawm cov tshuaj basophilic.
Kev tsim kho
Myelinated paj fibers muaj xws li:
- Axon, uas nyob hauv nruab nrab.
- Myelin sheath. Nws npog lub tog raj kheej axial.
- Schwann plhaub.
Lub tog raj kheej axial muaj cov neurofibrils. Lub myelin sheath muaj ntau yam lipoids uas tsim myelin. Qhov kev sib xyaw no tseem ceeb heev hauv kev ua haujlwm ntawm lub paj hlwb. Hauv particular, qhov ceev ntawm excitation yog nqa tawm raws cov hlab ntsha fibers nyob ntawm nws. plhaub,tsim los ntawm kev sib tshuam kaw lub axon nyob rau hauv xws li ib txoj kev uas qhov khoob yog tsim, uas yog hu ua nodes ntawm Ranvier. Hauv lawv cheeb tsam, lub tog raj kheej axial yog nyob rau hauv kev sib cuag nrog Schwann plhaub. Ib ntu fiber ntau yog nws qhov sib txawv, uas nyob nruab nrab ntawm ob qhov ntawm Ranvier. Hauv nws, ib tus tuaj yeem xav txog qhov tseem ceeb ntawm Schwann plhaub. Nws nyob ze ntawm qhov nruab nrab ntawm ntu. Nws yog surrounded los ntawm protoplasm ntawm ib tug Schwann cell nrog myelin cov ntsiab lus nyob rau hauv loops. Nruab nrab ntawm cov leeg ntawm Ranvier, myelin sheath tsis yog homogeneous. Nws muaj oblique notches ntawm Schmidt-Lanterman. Schwann sheath cells pib tsim los ntawm ectoderm. Nyob rau hauv lawv yog ib tug axon ntawm ib tug fiber ntawm peripheral paj hlwb, vim hais tias lawv yuav hu ua nws glial hlwb. Lub paj hlwb nyob rau hauv lub hauv paus system yog tsis muaj ntawm Schwann sheath. Hloov chaw, muaj cov ntsiab lus ntawm oligodendroglia. Lub unmyelinated fiber muaj tsuas yog axon thiab Schwann sheath.
Function
Lub luag haujlwm tseem ceeb uas cov paj hlwb ua yog innervation. Cov txheej txheem no muaj ob hom: impulse thiab impulseless. Hauv thawj kis, kev sib kis tau tshwm sim vim electrolyte thiab neurotransmitter mechanisms. Myelin plays lub luag haujlwm tseem ceeb hauv innervation, yog li qhov ceev ntawm cov txheej txheem no ntau dua nyob rau hauv myelinated fibers dua nyob rau hauv unmyelinated sawv daws yuav. Cov txheej txheem pulseless tshwm sim los ntawm axoplasmic tam sim no dhau los ntawm tshwj xeeb axon microtubules uas muaj trophogens (cov khoom uas muaj cov nyhuv trophic).
