Contraccion Muscular UNAB 2009

8/8/2019 Contraccion Muscular UNAB 2009

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ContracciContraccinnmuscularmuscular

Jorge Cajigal. MScJorge Cajigal. MSc


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Contenidos:1 . Ultraestructura del msculo

esqueltico2. Bioenergtica y Protenas

contrctiles3. Electrofisiologa (acoplamiento E-

C)4. Propiedades mecnicas

Msculo Liso

Smooth muscle fibres.Coloured scanning electronmicrograph (SEM) of a freeze-fractured bundleof smoothmuscle fibres(brown), with ablood vessel (pink, top left). Thefracture plane cuts across thesmoothmuscle fibres to revealthesmaller fibreswithinthelarger fibres. Smooth muscle isfound in places like the

digestive system and in bloodvessels. It is not under voluntarycontrol, instead being controlledby the autonommic nervoussystem and hormones. Itproduces slow, long-termcontractions.

Ultraestructura del msculoesqueltico


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Msculo CardiacoHeart muscle. Colouredtransmission electronmicrograph(TEM) of a sectionthrough healthyhuman heart (cardiac) muscle cells.Mitochondria(red) fill the cytoplasm(pink) and a large nucleus (green) isvisible at lower centre. The cells'musclefibres are divided intocontractile units called sarcomeresby dark discontinuous Z linesrunning from upper right tolowerleft. A capillary at lowerrightcontainsa red blood cell (redrectangle). The nucleus of theendothelial cell that lines thecapi l laryisabove the bloodcel l(green). Another capillary at bottomleft contains a white blood cell(yellow& p ink).. Magnification:x9,800 at 8x10" size.

Msculo Esqueltico

colouredtrans mission electronmicrograph (TEM) of a longitudinalsection through striatedskeletalmuscle. The striatedbanding-pattern of themuscle f ibri ls is seen.The f ibrils runin parallel(f romleft toright) and betweenth em runssarcoplasmic reticulum (SR) thattransmits nerve impulses to thefibrils. Here, the SR contains manymitochondria. Within each fibrilarecontractile units called sarcomeres

separated by lines. A sarcomerehas proteinfilaments of myosinandactinthat slide overeach other,thereby causing the wholemuscleto contract. Skeletal muscleisresponsiblefor voluntary musclemovement in the body.

Skeletal muscle. Colouredscanningelectron micrograph(SEM) of skeletal (striated) musclefibres. Eachmuscle fibre (greenbundle) consists of a number ofsmaller vertical strands calledmyofibrils enclosedby supportiveconnectivetissue (blue). Themyofibrils are crossed bytransverse tubulesand eachmyofibril is made up of manycontractile units called sarcomeres.Sarcomeres contain proteinf ilaments of myosin andactin whichcan slide over one another,allowing the muscle to contract.Skeletalmuscleis under theconsciouscontrol of the brain.Magnificationunknown.


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? Cookedbeef. Colouredscanning electronmicrograph(SEM) of thesurface of a pieceof cooked roast beef (boughtfrom a supermarket), showingdetails of theparallel musclefibres (top), a featureof skeletalmuscle. Details of striations(banding along each fibre) areevident, though a fine layer offat, deposited on the surfaceduring the cooking processcovers muchof this detail.Magnification: x20 at 6x4.5cmsize.

La Fibra (clula) Muscular


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Organization of Myofilaments in Skeletal Muscle

Fig. 2 StriatedSkeletal Muscle Tissue (x 97,900) illustratesmyofibrils in transversesection. A section throughthe end oftheA -band;i tis possible toobserve many transverselysectionedmyosinmyofilaments. The smalleractinmyofilamentsare arrangedinsucha waythatsi xactinmyofilamentssurrounda single myosinmyofilament. Extremelythinfilaments appearto interconnect(arrows)theactin andmyosinmyofilamentsin someareas, andrepresent theglobular heads ofthemyosin molecules.Mitochondrea(M) andprofiles ofth esarcoplasmicreticulum (SR) are i ncludedin Fig. 2. Themyofibril onthe right istransverselysectionednear the end of theH-band;about 400 myosinmyofilamentsare presentin thissection. At thisplane ofsectioning, mostofthe black dotsrepresentmyosin myofilaments, andonlya few actinmyofilamentsare visible in thelower left portionofthemicrograph.

A fiber in a large muscle like the

gastrocnemiusis composed of (on average) 2000

sarcomeres

Each sarcomere

is composed of around 1000 myofibrils

Each myofibril

contains around 1500 myosin and 3000 actin

myofilaments


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Teora del deslizamiento

Figure 12-3d

Ultrastructure of MuscleActin and myosin form crossbridges

Under light microscope one sees repeating light & dark bandsOne repeat pattern is a sarcomere

Z disks: attachment site for thin filamentsI band: lightest band, region only occupied by thin filamentsA band: darkest, entire length of thick filaments, overlap withthin filamentsH zone: Thick filaments only (center of A band)M line: attachment site for thick filaments

Bioenergtica y Protenascontrctiles

Figure 12-3e

Filamento gruesoMyosin are motor proteins. 250 myosinsjoin to form the thick filaments


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COO -

COO -

Myosin Light Chains (L1 and L2)

S-1S-2

HeavyMeromyosin

LightMeromyosin

TrypsinCleavage SitePapain Cleavage Site

?Myosin is a dimer consisting of two globular heads and a

supercoiled tail

Structure of the Thick Filament

L1

L1

L2

L2

?A set of light chains are associated with each globular head

?Globular myosin heads exhibit:

1) intrinsic ATPaseactivity2) actin binding site

Myosin

Filamento delgado?Thin filaments are actin chains and

regulatory proteins

Troponin-C

Structure of the Thin Filament

1) F-actin - a polymer of many G-actin monomers

F-Actin[

Tropomyosin

Troponin-I

Troponin-T

G-Actin monomer

2) Tropomyosin - lies in the groove between F-actin strandsand blocks myosin binding sites on actin

3) Tn-T: Affinity for tropomyosin4) Tn-I: Affinity for actin & inhibits actomyosin interaction5) Tn-C: Affinity for calcium

A complex of multiple interacting proteins:

1 pN


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Electrofisiologa (acoplamientoExitacin- Contraccin)


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ETAPAS DE LA CONTRACCINMUSCULAR

1. Descarga de la motoneurona

2. Liberacin del NT acetilcolina a la placa terminal3. Unin de la acetilcolina a sus receptores

4. Aumento de la conductancia de iones N a+ y K+ enla placa terminal

5. Generacin del potencial de accin en las fibrasmusculares

6. Liberaci n de Ca2+ desde el RS y difusi n hacialos filamentos delgados (Actina) y gruesos(Miosina)

7. Unin del calcio a la Troponina C8. Formaci n de puentes cruzados entre Actina y

Miosina

ETAPAS DE LA CONTRACCIN

MUSCULAR II

9. Deslizamiento de los filamentos delgados sobrelos gruesos, (Actina sobre Miosina)produciendo el acortamiento del Sarcmero.

10. Relajacin11. Bombeo de Ca2+ (ATP) de regreso al retculo

sarcoplsmico

12. Liberacin de Ca2+ proveniente de la Troponina

13. Suspensin de la interaccin entre losfilamentos de Actina y Miosina


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Propiedades mecnicas

De la protena a la fuerza externa

Clasificacin de la Fuerza Muscular

ComponentesComponentescelulares de la Fuerzacelulares de la Fuerza

?? ContrContrctilctil.sarc.sarcmeromero?? ElElsticostico..elastina, titina..elastina, titina

?? ReflejoReflejo.propioceptores.propioceptores

TIPOS DE CONTRACCINMUSCULAR

?CONTRACCIN DINAMICA(ISOTNICA)

a) CONCNTRICAb) EXCNTRICA

?CONTRACCIN ISOMTRICA?CONTRACCIN ISOCINTICA


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Figure 12-6

Titin and Nebulin


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La unidad Motora


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Motor Unit Recruitment

Motor neurons

Muscle Fibres

Muscle tension can be

increased by increasing

the number of motorunits that are active.


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YelenaYelena IsinbayevaIsinbayeva: 27a: 27aos, 1,74 yos, 1,74 y65 Kg.65 Kg. sentadilla 200sentadilla 200 KgKg CUERPO HUMANO POSEE:CUERPO HUMANO POSEE:

?250.000.000 de fibras muscularesesquelticas

?420.000 UM?600 fibras / UM en PROMEDIO

?UM pequeas = 10 fibras / MU?UM grandes = 2000 fibras / MU


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610445tibialis anterior

1720580gastrocnemius

595133opponens pollicis

11098first lumbrical

340119first dorsalinterosseous

390330brachioradialis

750774biceps brachii

fibers/motor

unit

number of alpha motor

axonsMuscle RegulaciRegulacin de la Fuerza Muscularn de la Fuerza MuscularEl cerebro combina dosEl cerebro combina dosmecanismos de control paramecanismos de control pararegular la fuerza de un mregular la fuerza de un msculosculoaislado:aislado:

?Reclutamiento?Frecuencia de descarga

(2) Temporal Summation

? A single twitch produces only ~20% of the

maximal possible tension? Contractions are additive if a second stimulus is

delivered prior to termination of the previous one

? At a certain frequency, the contractions fuse

together as a continuous contraction or tetanus

SingleTwitch

100 ms

TwitchSummation

Tension

AP

Tetanizacin y generacin de

fuerza muscular


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En la carrera de velocidadhay tiempo suficiente para

lograr una tetanizacin mxima de las UM?Por qu?

Maxima tetanizacin +

maximo reclutamiento

Clasificacin de fibrasmusculares

Principales diferencias

escasaabundanteMioglobina

discreta o escasabuena u ptimaResistencia a lafatiga

elevadabajaVelocidad decontraccin

pocosmuchosCapilares

dimetro mayorms finasDimensiones

fibras de tipo IIfibras rpidasFTFfibras blancas

fibras de tipo Ifibras lentasSTFfibras resistentes

Sinnimos

FIBRAS PLIDASFIBRASROJAS

Entre las fibras plidas, en cualquiercaso, se pueden distinguir algunossubtipos, los principales de losmismos son estos dos:

- Fibras de metabolismo glucoltico (IIb), queestn especializadas en la generacin rpidade ATP anaerbico

-Fibras de metabolismo oxidativo-glucoltico (IIa), son intermedias, porque seasemejan un poco a las fibras rojas y blancas

3763

Corredores de velocidady Saltadores

4555Halterofilistas

4555Atletas masculino nvelmdio fondo

7426Nadadores

8218Corredores de maratn

% fibraslentas

% de fibrasrpidas

CATEGORIA DEATLETA


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Fibras rpid as(ordem

decrescente)

Orbicular dos olhos12

Trceps braquial11

Esternocleidomast

ideo10

Quadrceps9

Bceps braquial8

Gastrocnmio7

Deltide6

Fbular longo5

Bceps femoral4

Tibial anterior3

Adutorpolegar2

Sleo1

Fibras lentas(ordem

decrescente)MsculosOrdem

Muscle Fiber Types

There are four different types of musclefibers:

?

?Type Ifondo

?Type IIAmixto

?Type IIBvelocidad - Fza?Type IICculturismo

PocasNormalNormalMuchasMitocondrias

Peq ueaGrandeGrandeGrandeIrrigacin

5,2902,8902,8901,730Tamao 2

50-10015-4015-405-15Frecuencia decontraccin Hz

BajaMediaAltaMuy altaResistencia afatiga

30-130 g13-40 g5-55 g2-13 gMxima tensi ntetnica

20-47 ms33-40 ms30-55 ms60-110 msTiempo decontraccin

Baja---------Alta[Triglicridos]

AltoAltoMedioBajo[Glucgeno]

AltaAltaAltaMedia[FosfoCreatna]

AltaMediaAltaMedia[ATP]

AltaAltaAltaBajaActividad de lasenzimas

glucolticas

BajaMediaMedia/altaAltaActividad de lasenzimas oxidativas

AltaAltaAltaBajaActividad ATPasica

Tipo IIbTipo IIcTipo IIaTipo I

Caption: Glycogengranules (small dark dots) incardiac muscle, colouredtransmission electronmicrograph (TEM). Glycogenis the polysaccharide thatconstitutes thestorageformof carbohydratein animalcells. Glycogenis brokendowninto glucose and theenzymatic degration ofglucose in turn provides

ene rgy. Endoplasmicreticulumis also seen(parallel bands).


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ElectronElectron micrographmicrographdemonstratingdemonstrating normalnormal musclemuscle vs. (B)vs. (B) musclemuscle thatthat hashas

undergoneundergone eccentriceccentric injuryinjury NoteNote thethe lossloss ofof ZZ--diskdisk alignmentalignment..

Figure 3:Desmin immunohistochemical staining of anormal muscle (A) and a muscle that has undergone

eccentricinjury (B). Whilethe normal muscle exhibits evenstaining in all cells, the eccentricallyinjuredmusclehas

cells that demonstrate desmin loss.

PatrPatrn de reclutamiento den de reclutamiento deCostillCostill

% de fibras musculares% de fibras musculares

% de fuerza m% de fuerza mximaxima

F IF I

FF IIaIIa

FF IIbIIb

Es posible reclutar fibras tipoIIB de forma especfica?

SISICon la fuerza explosiva (por ejm lossaltos y lanzamientos al mximo)


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Entrenamiento y fibrasEntrenamiento y fibras

muscularesmusculares

Fibra IFibra I

Fibra IIFibra II

Entrenamiento de fuerzaEntrenamiento de fuerza

inadecuadoinadecuado para lapara lavelocidadvelocidad

Fibra IFibra I

Fibra IIFibra II

Entrenamiento de fuerzaEntrenamiento de fuerzaadecuadoadecuado para la velocidadpara la velocidad

Fibra IFibra I

Fibra IIFibra II

Contraccion Muscular UNAB 2009

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