Lub mechanism ntawm nqaij contraction. Lub zog thiab cov khoom ntawm skeletal leeg

Nqaij contraction - yog ib tug complex txheej txheem uas muaj ib tug xov tooj ntawm theem. Lub ntsiab Cheebtsam ntawm no yog myosin, actin, troponin, tropomyosin thiab actomyosin, thiab calcium ions thiab cov tebchaw uas muaj kev nqaij zog. Xav txog cov hom thiab mechanisms ntawm nqaij contraction. Cia peb kawm, los ntawm uas lawv ua thiab cov kauj ruam tsim nyog rau cov cyclical txheej txheem.

nqaij

Nqaij ua ke rau hauv pab pawg, uas muaj tib lub mechanism ntawm nqaij contraction. Los ntawm tib token lawv raug muab faib ua 3 hom:

• striated nqaij ntawm lub cev;
• striated cov nqaij ntshiv ntawm lub atria thiab ventricles ntawm lub siab los;
• tus nqaij nruab nrog cev, cov hlab ntsha thiab daim tawv nqaij.

Striated nqaij yog ib feem ntawm lub licas, ua ib feem ntawm nws, vim hais tias nyob rau hauv tas li ntawd mus rau lawv, qhov no muaj xws li tendons, ligaments, cov pob txha. Thaum siv cov mechanism ntawm nqaij contraction, ua cov nram qab no kev paub tab thiab kev khiav dej num:

• lub cev txav;
• lub cev qhov chaw uas nyuam qhuav txav los txheeb ze rau txhua tus lwm yam;
• lub cev yog txaus siab nyob rau hauv qhov chaw;
• Thaum tshav kub kub yog generated;
• cortex yog tshuab txais los ntawm afferent mus rau lub txais liaj teb ntawm nqaij.

Ntawm tus nqaij yog:

• lub cev muaj zog apparatus ntawm lub hauv nruab nrog cev, uas muaj xws li lub bronchial tsob ntoo, lub ntsws thiab lub digestive raj;
• lub lymphatic thiab lub plawv systems;
• system urogenital kabmob.

physiological zog

Zoo li tag nrho cov vertebrates nyob rau hauv tib neeg lub cev muaj peb tseem ceeb tshaj plaws thaj chaw ntawm skeletal leeg fibers:

• contractility - txo thiab hloov cov voltage thaum zoo siab heev;
• conductivity - zog muaj peev xwm thoob plaws hauv lub fiber;
• excitability - teb rau ib tug stimulus los hloov cov daim nyias nyias tej zaum thiab ion permeability.

Nqaij yog pog thiab pib tsis kam los ntawm paj impulses los ntawm qhov chaw. Tab sis nyob rau hauv tej yam kev mob dag siv hluav taws xob stimulation. Cov nqaij yuav ces yuav khaus ncaj qha (direct stimulation) los yog los ntawm lub paj innervating nqaij (indirect stimulation).

hom ntawm tej qhov nqaij ntuag

Lub mechanism ntawm npag contraction txhais tau tias hloov dua siab tshiab ntawm tshuaj muaj zog rau hauv txhua yam kev ua hauj lwm. Qhov no txoj kev muaj peev xwm yuav ntsuas experimentally nrog Qav: nws plab hlaub nqaij load tsawg luj, thiab ces chim siab electroimpulses teeb. Cov yuav txo tau, nyob rau hauv uas cov nqaij yuav luv luv, hu ua isotonic. shortening tshwm sim thaum isometric contraction. Tendons tsis pub txoj kev loj hlob ntawm nqaij muaj zog zog. Lwm auksotonichesky mechanism ntawm nqaij contraction yuav tej yam kev mob ntawm khaus kev nyuaj siab thaum cov nqaij shortens tsawg heev txoj kev, thiab lub hwj chim mus cuag ib tug tshaj plaws.

Tus qauv thiab innervation ntawm skeletal leeg

Lub striated skeletal leeg muaj xws li ib tug ntau yam ntawm fibers nyob rau hauv connective cov ntaub so ntswg thiab tsau mus rau lub tendons. Nyob rau hauv ib co nqaij fibers cov txheej txheem thaum uas tig mus rau qhov ntev axis, thiab nyob rau hauv lwm tus neeg lawv yog oblique views, raug txuas mus rau ib tug central txog leeg tyazhu thiab pinnate hom.

Lub ntsiab feature ntawm lub fiber yog sarcoplasm loj zoo threads - myofibrils. Lawv yog cov kaj thiab tsaus ntuj nti chaw alternating nrog txhua lwm yam, thaum lub sij hawm uas nyob ib sab striated fibers yog dej ntws yaug - nyob rau hauv tus ntoo khaub lig-section. Qhov no los tau nyob rau hauv tus ntoo khaub lig-banding nyob ib ncig ntawm cov nqaij fibers.

Sarcomere yog ib tug complex, tsaus ntuj nti thiab ob lub teeb disks, thiab nws delimited Z-zoo li tus kab. Sarcomeres - ib tug contractile apparatus ntawm nqaij. Nws hloov tawm hais tias lub contractile nqaij fiber muaj:

• contractile apparatus (myofibrils system);
• trophic apparatus nrog mitochondria, Golgi complex thiab tsis muaj zog endoplasmic reticulum ;
• daim nyias nyias ntaus ntawv;
• siv apparatus;
• tshee apparatus.

Nqaij fiber yog muab faib ua 5 qhov chaw nrog lawv lug thiab kev khiav dej num, thiab yog ib feem ntawm cov nqaij cov ntaub so ntswg.

innervation

Qhov no txoj kev nyob rau hauv striated nqaij fibers pom tau hais los paj fibers, namely axons ntawm lub cev muaj zog neurons ntawm cov leeg nrob qaum thiab lub hlwb kav. Ib motoneuron innervate ob peb leeg fibers. Complex nrog ib tug motoneuron thiab innervated nqaij fibers hu ua neuromotor (HME) los yog ib tug lub cev muaj zog tsev (MU). Nruab nrab ntawm cov fibers, uas innervates ib motoneuron, characterizes lub DE nqaij, hu ua reciprocal innervation ceev. Cov yav tas yog cov coob nyob rau hauv cov nqaij, qhov twg me me taw thiab "nyias" (ob lub qhov muag, cov ntiv tes, tus nplaig). Nws tus nqi yog me me, nyob rau hauv tsis tooj, nyob rau hauv cov nqaij nrog ib tug "ntxhib" tsab ntawv tsa suab (e.g., npog tas ib ce).

Innervation yuav ua tau ib thiab ntau yam. Nyob rau hauv thawj rooj plaub no nws yog pom tau hais compact lub cev muaj zog txoj. Feem ntau nws yog raug rau cov loj lub cev muaj zog neurons. Nqaij fibers (hu ua nyob rau hauv cov ntaub ntawv no, lub cev, los yog ceev) generating PD (txiav txim potentials) uas siv rau lawv.

Ntau innervation tshwm sim, piv txwv li, nyob rau hauv lwm qhov muag nqaij. Qhov no yog tsis yog ib qho kev txiav txim tej zaum yog generated, txij thaum lub membrane tsis muaj electroexcitability sodium raws. Lawv faib thoob plaws hauv lub fiber depolarization ntawm lub synaptic txoj. Qhov no yog tsim nyog nyob rau hauv thiaj li yuav qhib lub mechanism ntawm nqaij contraction. Cov txheej txheem no tsis yog raws li ceev ceev raws li nyob rau hauv thawj cov ntaub ntawv. Yog li ntawd, nws yog hu ua qeeb.

Tus qauv ntawm lub myofibrils

nqaij fiber kev tshawb fawb nqa tawm hnub no nyob rau hauv lub hauv paus ntawm X-hluav taws xob diffraction, electron microscopy, thiab histochemical txoj kev.

Nws yog xam hais tias nyob rau hauv txhua myofibril, lub lub cheeb ntawm uas yog 1 micron, muaj xws li kwv yees li 2,500 protofibrils, i.e. elongated polymerized molecules cov nqaijrog (actin thiab myosin). Actin protofibrils ob zaug thinner myosin. Thaum so, cov nqaij yog nyob li hais tias tus actin filament tswv yim txeem mus rau hauv tej qhov chaw ntawm lub myosin protofibrils.

Ib tug nqaim sawb ntawm lub teeb nyob rau hauv lub disk A yog pub dawb los ntawm actin filaments. Ib tug membrane Z tuav lawv ua ke.

Nyob rau myosin filaments muaj transverse protrusions mus txog 20 nm, nyob rau hauv lub taub hau uas yog hais txog 150 myosin molecules. Lawv ncaim biopolyarno, thiab txhua tus lub taub hau myosinic txuas mus rau lub actin filament. Thaum muaj kev nyuaj siab nyob rau hauv filaments ntawm actin chaw myosin, actin filament yog nyob ze rau qhov chaw ntawm lub sarcomere. Thaum kawg ntawm lub myosin filaments mus txog txoj kab Z. Ces lawv coj ib tug tag nrho sarcomere, thiab actin yog cov lawv. Nyob rau tib lub sij hawm kuv tsav tsheb ntev yog txo, thiab nyob rau hauv lub kawg nws disappears nkaus, ua ke nrog dab tsi rau hauv txoj kab Z yuav thicker.

Yog li, raws li lub hom phiaj ntawm tsiv yarns, vim txo ntev ntawm cov nqaij fibers. Qhov kev tshawb xav, hu ua "iav", yog tsim los ntawm Huxley thiab Hanson nyob rau hauv nruab nrab ntawm lub thib nees nkaum caug xyoo.

Mechanism ntawm nqaij fiber contraction

Lub ntsiab kev tshawb xav yog hais tias tsis muaj filament (myosin thiab actin) yog zog. Lawv ntev tseem unchanged thiab nqaij nro. Tab sis bundles ntawm nyias filaments, slipping, mus ua lub tuab filaments, decreases cov neeg kawm ntawv ntawm sib tshooj, thiaj li muaj ib tug yuav txo tau.

Lub molecular mechanism ntawm npag contraction yog raws li nram no los ntawm zawv zawg actin filaments. Myosin lub taub hau kev cob cog rua protofibrils nrog actin. Nrog lawv slopes muaj zawv zawg, txav actin filament rau qhov chaw ntawm lub sarcomere. Vim lub bipolar lub koom haum ntawm myosin molecules rau ob tog ntawm lub filaments, lub tej yam kev mob rau zawv zawg ntawm actin filaments nyob rau hauv txawv kev qhia.

Thaum nqaij so myosin lub taub hau tsiv deb ntawm lub actin filaments. Nrog ib qho yooj yim ris hauv qab so nqaij nro tsis kam tsawg npaum li cas. Yog li ntawd, lawv yog passively lengthened.

yuav txo tau cov kauj ruam

Lub mechanism ntawm npag contraction yuav luv luv faib mus rau hauv lub nram qab no theem:

1. Nqaij fiber yog tsa thaum muaj ib tug txiav txim tej zaum yog nkag los ntawm lub cev muaj zog neurons ntawm lub synapses.
2. Qhov kev txiav txim tej zaum yog generated nyob rau hauv daim nyias nyias ntawm cov nqaij fiber, thiab ces kis mus rau lub myofibrils.
3. Accomplished electromechanical khub sawv cev ib tug hloov dua siab tshiab ntawm hluav taws xob mus rau hauv cov neeg kho tshuab zawv zawg PD. Qhov no tas yuav calcium ions.

calcium ions

Rau ib tug zoo kev nkag siab ntawm tus txheej txheem ntawm fiber ua kom cov calcium ions yog yooj yim mus xav txog cov qauv ntawm cov actin filament. Nws ntev yog hais txog 1 micron, thickness - ntawm 5 mus rau 7 nm. Qhov no yog ib khub ntawm cov threads, uas zoo li lub actin monomer. Kwv yees li txhua txhua 40 nm ntawm no yog kheej kheej troponin molecule, thiab ntawm lub chains - tropomiozinovye.

Thaum calcium ions yog tsis tuaj kawm ntawv, piv txwv li myofibrils so ntev tropomiozinovye molecules thaiv lub Symptoms ntawm actin chains thiab myosin choj. Tab sis thaum tshuab txais calcium ions tropomiozinovye molecules tog tob thiab qhib qhov chaw.

Ces tus myosin choj uas txuas mus rau actin filaments thiab ATP tawg thiab npaj nqaij muaj zog. Qhov no yog tau vim yog tej yam ntawm calcium troponin. Nyob rau hauv no molecule rau tom kawg yog deformed, li no thawb lub tropomyosin.

Thaum cov nqaij yog relaxed, nws yog 1 gram ntub hnyav muaj ntau tshaj li 1 mmol ntawm calcium. Calcium ntsev yog raug rho tawm thiab tshwj xeeb cia cov chaw. Txwv tsis pub, cov nqaij ntshiv yuav yeej ib txwm tsis yeem.

calcium tso raws li nram no. Nyob rau hauv cheeb tsam sib txawv ntawm cov diaphragm mob hlwb nyob rau hauv lub fiber yog hlab los ntawm kev uas muaj ib tug kev twb kev txuas nrog cov ib puag ncig sab nraum lub hlwb. Nws yog ib tug system ntawm transverse tubules. Ib tug system yog perpendicular mus rau lub longitudinal xaus ntawm uas - hlwv (davhlau ya nyob twg) tso tsheb hlau luam cov txheej txheem ntawm nyob rau hauv ze sib thooj mus rau lub transverse diaphragms system. Ua ke tau triad. Nws yog nyob rau hauv vials muab calcium.

Txij li thaum PD yog faib mus rau hauv lub cell, thiab muaj ib tug electromechanical conjugation. Excitation penetrates rau hauv lub fiber kis mus rau hauv ib tug longitudinal system tawm calcium. Yog li txo mechanism yog nqa nqaij fibers.

3 txheej txheem nrog ATP

Nyob rau hauv lub sis ntawm ob strands nyob rau hauv lub xub ntiag ntawm calcium ions ib tug txiav txim lub luag hauj lwm rau ATP. Thaum siv cov mechanism ntawm nqaij contraction ntawm skeletal leeg, lub zog ntawm ATP yog siv mus rau:

• lag luam los ntawm sodium thiab potassium twj tso kua mis uas muaj ib qhov concentration ntawm ions;
• cov tshuaj rau txawv sab ntawm daim nyias nyias;
• zawv zawg filaments shortening myofibrils;
• Txoj hauj lwm calcium twj tso kua mis kuj mus so kom txaus.

ATP yog lub cell daim nyias nyias, cov filaments ntawm myosin thiab sarcoplasmic reticulum week. Enzymes zom thiab pov tseg ntawm myosin.

tau ntawm ATP

Nws yog lub npe hu hais tias myosin hau nrog actin thiab muaj ntsiab rau ATP cleavage. Xeem tshuab txais actin thiab myosin nyob rau hauv lub xub ntiag ntawm magnesium ions. Yog li ntawd enzyme cleavage yuav siv sij hawm qhov chaw thaum uas txuas mus rau actin myosin lub taub hau. Qhov ntau dua tus ntoo khaub lig-choj, cov splitting ceev yuav tsum muaj ntau.

ATP mechanism

Tom qab kawm tiav ntawm lub zog ntawm tus AFL molecule muab lub zog rau lub sib cais ntawm cov tshuaj tiv thaiv kev koom tes nyob rau hauv actin thiab myosin. Myosin lub taub hau cais, ATP yog cleaved rau ntsev thiab ADP. Tus tshiab kawg yog kev cob cog rua ATP molecule thiab lub voj voog resumes. Xws li yog cov mechanism ntawm nqaij contraction thiab so ntawm lub molecular theem.

Cov kev ua ntawm tus ntoo khaub lig-choj yuav kav tsuas yog raws li ntev raws li lub ATP hydrolysis tshwm sim. Yog hais tias koj thaiv cov enzyme choj yuav tsis tau daim ntawv dua.

Nrog rau qhov pib ntawm txoj kev tuag ntawm cov kab mob nyob rau theem ntawm ATP nyob rau hauv lub hlwb ntog thiab choj nyob twj ywm stably tsau mus rau lub actin filament. Yog li ntawd, yog cov theem ntawm rigor mortis.

ATP resynthesis

Resynthesis tau muab los siv nyob rau hauv ob txoj kev.

Los ntawm enzymatic hloov lwm lub tsev ntawm phosphate pab pawg neeg los ntawm creatine phosphate rau ADP. Txij li thaum stocks ntawm creatine nyob rau hauv lub cell ntau npaum li cas ATP resynthesis siv heev sai sai. Nyob rau tib lub sij hawm, los ntawm cov oxidation uas pyruvic acid thiab lactic acid resynthesis yuav tau qeeb.

ATP thiab CP yuav ploj kiag li yog tias resynthesis yog tawg tshuaj lom. Ces tus calcium twj tso kua mis nres ua hauj lwm, uas ua rau cov leeg yog irreversibly txo (ie tuaj contracture). Yog li, tawg mechanism ntawm npag contraction.

physiology txheej txheem

Nyob rau hauv txoj kev, peb nco ntsoov hais tias tus yuav txo tau ntawm nqaij fibers yog zog nyob rau hauv txhua ntawm myofibrils sarcomeres. Lub filaments ntawm myosin (tuab) thiab actin (nyias) kev cob cog rua xaus nyob rau hauv ib tug xoob lub xeev. Tab sis lawv pib zawv zawg zog mus rau txhua lwm yam thaum siv mechanism ntawm nqaij contraction. Physiology (luv luv) piav txog cov txheej txheem thaum tus myosin yog tso tawm lub zog yuav tsum tau mus hloov ATP rau ADP. Yog li myosin kev ua si yuav tsum pom tau hais tsuas yog thaum ib tug txaus cov ntsiab lus ntawm calcium ions noog nyob rau hauv lub sarcoplasmic reticulum.