MIDTERM- MUSCLE

• MUSCULAR SYSTEM FUNCTION

  ·       Producing body movement

  ·       Stabilizing body position

  ·       Storing and moving substance within the body

  Generating heat
• PROPERTIES OF MUSCULAR TISSUE

  ELECTRICAL EXCITABILITY

  CONTRACTILITY

  EXTENSIBILITY

  ELASTICITY
• 3 LAYERS OF CONNECTIVE TISSUE

  EPIMYSIUM

  PERIMYSIUM

  ENDOMYSIUM
• SKELETAL MUSCLE LEVEL OF ORGANIZATION

  SKELETAL MUSCLE

  FASICLE

  MUSCLE FIBER

  MYOFIBRIL

  FILAMENTS
• SKELETAL MUSCLE


  Organ made up of fascicles than contain muscle fibers (cells), blood vessels, and nerves; wrapped in epimysium
• FASICLE


  Bundle of muscle fibers wrapped in perimysium
• MUSCLE FIBER


  Long cylindrical cell covered by endomysium and sarcolemma: contains sarcoplasm, myofibrils, many peripherally located nuclei, mitochondria, transverse tubules, sarcoplasmic reticulum, and terminal cisterns. The fiber has a striated appearance
• MYOFIBRIL


  Threadlike contractile elements within sarcoplasm of muscle fiber that extend entire length of fiber; composed of filaments
• FILAMENTS


  Contractile proteins within myofibrils that are two types; thick filaments composed of myosin and thin filaments composed of actin, tropomyosin, and troponin; sliding of thin filaments pas thick filaments produces of muscle shortening
• COMPONENTS OF SACROMERE

  Z DISCS

  A BAND

  H ZONE

  M LINE
• Z DISCS


  Narrow, plate-shaped regions of dense material that separate one sarcomere from the next
• A BAND


  Dark, middle part of sarcomere that extends entire length of thick filaments and includes those parts of thin filaments that overlap thick filaments
• I BAND


  Lighter, less dense area of sarcomere that contains remainder of thin filaments but no thick filaments. A Z disc passes through center of each I band.
• H ZONE


  Narrow region in center of each A band that contains thick filaments but no thin filaments
• M LINE


  Region in center of H zone that contains proteins that hold thick filaments together at center of sarcomere
• TYPE OF PROTEIN

  CONTRACTILE PROTEIN

  REGULATORY PROTEIN

  STRUCTURAL PROTEIN
• CONTRACTILE PROTEIN


  PROTEINS THAT GENERATE FORCE DURING MUSCLE CONTRACTIONS
• REGULATORY PROTEINS


  HELP SWITCH MUSCLE CONTRACTION PROCESS ON AND OFF
• STRUCTURAL PROCESS


  Proteins that keep thick and thin filaments of myofibrils in proper alignment, give myofibrils elasticity and extensibility, and link myofibrils to sarcolemma and extracellular matrix
• CONTRACTILE PROCESS


  MYOSIN

  ACTIN
• MYOSIN


  Contractile protein that makes up thick filament; molecule consists of a tail and two myosin heads, which bind to myosin- binding sites on actin molecules of thin filament during muscle contraction
• ACTIN


  Contractile protein that is the main component of thin filament; each actin molecule has a myosin-binding site where myosin head of thick filament binds during muscle contraction
• REGULATORY PROTEIN


  TROPOMYOSIN

  TROPONIN
• TROPOMYOSIN


  Regulatory protein that is a component of thin filament; when skeletal muscle fiber is relaxed, tropomyosin covers myosin- binding sites on actin molecules, thereby preventing myosin from binding to actin.
• TROPONIN


  Regulatory protein that is a component of thin filament; when calcium ions (Ca) bind to troponin, it changes shape; this conformational change moves tropomyosin away from myosin-binding sites on actin molecules, and muscle contraction subsequently begins as myosin binds to actin
• STRUCTURAL PROTEIN


  TITIN

  A-ACTININ

  MYOMESIN

  NEBULIN

  DYSTROPHIN
• TITIN


  Structural protein that connects Z. disc to M line of sarcomere, thereby helping to stabilize thick filament position, can stretch and then spring back unharmed, and thus accounts for much of the elasticity and extensibility of myofibrils
• A-ACTININ


  Structural protein of Z discs that attaches to actin molecules of thin filaments and to titin molecules
• MYOMESIN


  Structural protein that forms M line of sarcomere; binds to titin molecules and connects adjacent thick filaments to one another.
• NEBULIN


  Structural protein that wraps around entire length of each thin filament, helps anchor thin filaments to Z. discs and regulates length of thin filaments during development
• DYSTROPHIN


  Structural protein that links thin filaments of sarcomere to integral membrane proteins in sarcolemma, which are attached in turn to proteins in connective tissue matrix that surrounds muscle fibers; thought to help reinforce sarcolemma and help transmit tension generated by sarcomeres to tendons
• contraction cycle


  atp hydrolysis

  attachment of myosin to actin to form cross bridges

  power stroke

  detachment of myosin from actin
• neuromuscular junction

  release of acetylcholine

  activation of ash receptors

  production of muscle action potential

  termination of ash activity
• types of muscle contraction

  concentric

  eccentric

  isometric
• concentric


  shortening of muscle length during contraction
• eccentric


  the length of the muscle increases during contraction
• isometric


  muscle length remains uncharged during contraction
• motor unit


  a single motor neuron and all the muscle fiber it innervates