Muscular Anatomy & Physiology

• The skeletal muscle is the most abundant tissue in the body, accounting for about half of its weight.
• Skeletal muscles are attached to bones by tendons.
• Muscle fibers have long cylindrical cells with many nuclei at their ends.
• Each fiber contains myofibrils that contain actin and myosin filaments.
• Each fiber contains myofibrils that contain actin and myosin filaments.
• Actin filaments slide over myosin filaments during contraction.
• Myofilaments contract when stimulated by nerve impulses.
• A motor unit consists of one motor neuron and all the muscle fibers it innervates.
• Myofilaments slide past one another during contraction.
• Myofilaments slide past one another during contraction.
• Motor units can be recruited individually or as groups depending on the intensity of contraction needed.
• Motor units can be recruited individually or as groups depending on the intensity of contraction needed.
• Actin and myosin filaments overlap when relaxed.
• Actin and myosin filaments overlap when relaxed.
• Endomysium


  Delicate connective tissue membrane that covers skeletal muscle fibers

  
• Epimysium


  coarse sheath covering the muscle as a whole

  
• Perimysium


  Tough connective tissue binding together fascicles

  
• Functions of skeletal muscle tissue

  Excitability(irritability) , Contractility , Extensibility
• Excitability (irritability)


  Ability to be stimulated
• Contractility


  Ability to contract , or shorten , and produce body movement
• Extensibility


  Ability to extend , or stretch , thereby allowing muscles to return to their resting length
• Myofibrils


  Numerous fine fibers packed close together in sarcoplasm , each contains thousands of thick and thin myofilaments

  
• Muscle cells called

  Fibers
• Sarcomere


  Smallest contractile functional unit of muscle fibers , segment of myofibril between two successive Z disks , Each myofibril consists of many of it

  
• T-Tubules location and function

  Wrapped around the Sarcoplasmic Reticulum and allows nerve impulses traveling along the sarcolemma to move deeper into the cell

  
• Sarcolemma


  Plasma membrane of muscle fibers

  
• Sarcoplasmic Reticulum content and function

  Contains T-Tubules , its membrane always pumps calcium ions from the sarcoplasm and stores the ions within its sacs for later release

  
• What Are T-Tubules?

  Network of tubules and sacs found within muscle fibers

  
• Connective tissue components

  Endomysium , Perimysium , Epimysium
• Sarcoplasm


  Organelle of the muscle fiber that stores calcium , Releases calcium for muscles via nervous stimulation from motor neurons.

  
• A Band


  Striated muscle dark stripes

  
• H Band


  Light color , runs across the midsection of each A band

  
• I Band


  Light color stripes , that have dark Z disk extending across their center

  
• Z Disks

  Dark color , extends across the center of each I band

  
• What makes up the Myofilament?

  four different kinds of protein molecules

  
• Four kinds of protein molecules that makes up myofilaments

  Myosin , Actin , Tropomyosin , Troponin

  
• Myosin


  THICK filament , Myosin "heads" chemically attracted to actin molecules , when these "heads" attached to actin they called "cross bridges"
• Actin

  Globular protein that forms two fibrous strands twisted around each other to form the bulk of the THIN filament
• Tropomyosin


  Protein that BLOCKS the active sites on actin molecules
• Troponin


  Protein that HOLDS tropomyosin molecules in place