EXSC%223%Exam%3:%CH%9&23%Study%Guide%Exam%material:%9.1-9.5,%9.7,%9.9,%23.1-23.10%%Learning%objectives%for%chapters%9.1%Learning%objectives%Compare%and%contrast%the%three%basic%types%of%muscle%tissue.%• Skeletal%muscle%o Attach%to%and%cover%skeleton%o Voluntary%muscle:%under%conscious%control%o Responsible%for%body%mobility%o striated%• Cardiac%muscle%o Only%located%in%the%heart%o Striated%o Involuntary:%contracts%and%relaxes%on%its%own%o Contraction%rate%determined%by%pacemaker%• Smooth%muscle%o Located%in%walls%of%hollow%visceral%organs%(stomach,%bladder,%respiratory%passageways)%o No%striations%o Elongated%cells%o Involuntary%List%four%important%functions%of%muscle%tissue.%4%functions%of%muscle%1. Produce%movement%2. Maintain%posture%and%body%position%3. Stabilize%joints%4. Generate%heat%%9.2%Learning%objectives%Describe%the%gross%structure%of%a%skeletal%muscle.%• Each%skeletal%muscle%is%an%organ%o Tissues%present:%§ Muscle%fibers%§ Blood%vessels%§ Nerve%fibers%§ Connective%tissue%• Nerve%and%blood%supply%o In%general,%1%nerve,%1%artery,%and%1+%veins%serve%each%muscle%§ Exit%or%enter%near%the%central%part%of%the%muscle%and%branch%throughout%o Supplied%with%nerves%because%voluntary%contraction%(unlike%cardiac%and%smooth%muscle)%o Rich%blood%supply%§ Lots%of%energy%needed%for%contraction%§ Needs%continuous%delivery%of%oxygen%and%nutrients%o Veins%remove%the%metabolic%wastes%to%keep%contractions%efficient%• Connective%tissue%sheaths%o Wrap%muscle%fibers%to%protect%them%and%keep%them%intact%o Epimysium%§ Outermost%connective%tissue%§ Dense%irregular%connective%tissue%§ Surrounds%whole%muscle%o Perimysium%§ Connective%tissue%surrounding%fascicles%• Fascicle:%bundle%of%muscle%fibers%§ Dense%irregular%connective%tissue%o Endomysium%§ Wispy%sheath%of%areolar%connective%tissue%§ Surrounds%each%individual%muscle%fiber%o They%are%all%continuous%with%one%another%and%with%the%tendons%(connect%muscle%to%bones)%• Attachments%o Direct/fleshy%attachments%§ Epimysium%(of%the%muscle)%fuses%with%the%periosteum%(of%the%bone)%or%the%perichondrium%(of%cartilage)%o Indirect%attachments%§ Muscle’s%connective%tissue%extend%beyond%the%muscle%(forming%a%tendon)%to%attach%it%to%bone%or%cartilage%§ More%common%because%of%durability%and%small%size%o Tendons%§ Mostly%made%of%tough%collagen%fibers%§ Withstand%abrasion%of%rough%bony%projetions%%9.3%Learning%objectives%Describe%the%microscopic%structure%and%functional%roles%of%the%myofibrils,%sarcoplasmic%reticulum,%and%T%tubules%of%skeletal%muscle%fibers.%• Skeletal%muscle%fiber%o Long,%cylindrical%cell%o Multiple%nuclei%o Sarcolemma=plasma%membrane%o Huge%cell-10x%bigger%than%normal%body%cell%o Sarcoplasm=cytoplasm%of%muscle%cell%o Glycosomes:%granules%of%stored%glycogen%that%provide%glucose%during%muscle%cell%activity%o Myoglobin:%red%pigment%that%stores%oxygen%o %3%specially%developed%organelles:%myofibrils,%sarcoplasmic%reticulum,%T%tubules%• myofibrils%o rodlike%organelles%that%run%parallel%to%the%length%of%the%muscle%fiber%o make%up%80%%of%the%cell’s%volume%o contains%sarcomeres,%which%contain%myofilaments%o striations%§ repeating%series%of%dark%and%light%bands%along%each%myofibril%• dark%A%bands%o H%zone:%lighter%region%in%its%midsection%§ M%line:%dark%line%that%bisects%the%H%zone%• light%I%bands%o Z%disc%(Z%line):%dark%area%that%runs%through%the%I%band%o Sarcomeres%§ Region%of%myofibril%between%two%Z%discs%§ Smallest%contractile%unit%of%a%muscle%fiber%§ Functional%unit%of%skeletal%muscle%§ Contains%an%A%band%in%between%two%I%bands%o Myofilaments%§ Thick%filaments%contain%myosin%• Extend%the%entire%length%of%the%A%band%• Connected%in%the%middle%of%the%sarcomere%at%the%M%line%§ Thin%filaments%contain%actin%• Extends%across%the%I%band%and%partway%into%the%A%band%• Anchored%by%the%Z%discs%o Molecular%composition%of%myofilaments%§ Muscle%contraction%is%dependent%on%the%myofilaments%§ Myosin%• Consists%of%2%heavy%and%4%light%polypeptide%chains%• Has%a%rod-like%tail%attached%by%a%flexible%hinge%to%two%globular%heads%§ Cross%bridge:%when%a%link%is%formed%between%thick%and%thin%filaments%during%contraction%§ Actin%• Contain%active%sites%for%myosin%heads%to%attach%to%during%contraction%• 2%intertwined%actin%filaments%form%backbone%of%thin%filament%• contain%regulatory%proteins%o tropomyosin%§ rod-shaped%protein%that%spirals%about%the%actin%core%§ stiffens%and%stabilizes%actin%§ when%muscle%fiber%is%relaxed:%blocks%myosin-binding%sites%on%the%actin%o troponin%§ globular%3%polypeptide%complex%• TnI:%inhibitory%subunit%that%binds%to%actin%• TnT:%binds%to%tropomyosin%and%helps%position%it%on%actin%• TnC:%binds%calcium%ions%• Sarcoplasmic%reticulum%and%T%tubules%o Regulate%muscle%contraction%o Sarcoplasmic%reticulum%§ Elaborate%smooth%ER%§ Surround%myofibrils%§ Most%SR%tubules%communicate%with%the%myofibril%at%the%H%zone%§ Terminal%cisternae%• Located%at%A%band-I%band%junctions%• Found%in%pairs%§ Regulates%intracellular%levels%of%ionic%calcium%• Stores%and%releases%it%when%muscle%fiber%is%stimulated%to%contract%o T%tubules%§ At%each%A%band-I%band%junction,%sarcolemma%protrudes%into%the%cell%interior%forming%a%tube%§ T=transverse%§ Increase%surface%area%§ Lumen%of%T%tubule%is%continuous%with%the%extracellular%space%§ Runs%between%a%pair%of%terminal%cisternae%(forming%a%triad)%§ Serve%as%a%rapid%communication%system%to%quickly%tell%the%terminal%cisternae%when%to%release%calcium%Describe%the%sliding%filament%model%of%muscle%contraction.%• Sliding%filament%model%of%contraction%o During%contraction,%the%thin%filaments%slide%past%the%thick%ones%so%that%the%actin%and%myosin%filaments%can%overlap%to%a%greater%degree%o In%a%relaxed%muscle%fiber:%thin%and%thick%filaments%overlap%only%at%the%ends%of%the%A%band%o As%a%muscle%cell%shortens:%§ I%bands%shorten%§ Distance%between%successive%Z%discs%shortens%§ H%zones%disappear%§ Contiguous%A%bands%move%closer%together%%9.4%Learning%objectives%Explain%how%muscle%fibers%are%stimulated%to%contract%by%describing%events%that%occ ur %at%the %neuromuscular%junction.%• the%nerve%stimulus%and%events%at%the%neuromuscular%junction%o somatic%motor%neurons:%nerve%cells%that%activate%skeletal%muscle%fibers%§ located%in%brain%and%spinal%cord%o