Contraccion Muscular UNAB 2009
Transcript of 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 electronmicr- ograph(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