Skeletal Muscle Tissue

Skeletal Muscle Tissue

1. Epimysium: Surrounds entire muscle, overcoat of dense irregular connective tissue.

2. Endomysium: Surrounds each muscle fiber, areolar connective tissue.

3. Perimysium: surrounds each fasicle: Dense Irregular connective tissue

4. Fasicle: grouped muscle fiber

5. Connective tissue: make up sheaths, when muscle contracts, sheaths are pulled and transmit bone force.

   • Sheaths hold muscle together and prevent bursting

6. Nerves: Voluntary m'vt is able via stimulation of muscle fibers by way of somatic muscle motor neuron

7. Blood Vessels(Muscle Capillaries) carry oxygen and nutrients remove metabolic wastes through veins.

8. Muscle Fiber

   • Sarcolemma is plasma membrane
     • T-Tubules: Extension of sarcolemma that protrudes deeply into the muscle cell.
   • Sarcoplasm is cytoplasm of muscle cell.
   • Myofibrils: bundle of contractile filaments
     • Myofilaments: are within sarcomeres and are the filaments of myofibrils.
       • Thick Filaments contain myosin and extend the length of A band. A band overlaps
         • Each Dark A band has a lighter region in midsection called H zone
           • Hzone does not overlap thin, appears less dense.
         • Myosin: contractile protein
           • Myosin Tail: consists of interwined helical polypeptide heavy chains. "Forearm."
           • Myosin Head: two; associated with light chains. "Fist"
             • Cross Bridges: During contraction myosin head groups link with actin to form cross bridges.
             • Myosin head swivel around their point of attachment and have ATPase function
             • Hinge: attaches each tail to two globular heads
       • Thin Filaments: Contain Actin and extend length of I band
         • Each I band has a midline interruption, darker area called Z disc
           • I band only thin filaments, does not overlap thick
         • Zdisc/line anchors thin filaments
         • Actin a contractile protein.
           • Troponin: binds to action via TnI. TnT binds to tropomyosin and helps position it on actin.
             • TnC binds to calcium
           • Tropomyosin: protein about the actin core that helps stiffen and stabilize it.
             • In relaxed muscle fiber, tropomyosin block myosinn binding sites on actin so myosin thick heads cannot bind to thin
     • Sarcomere: smallest contractile unit of muscle that extends from Zdisc to Zdisc
   • Sarcoplasmic Reticulum (SR) is specialized endoplasmic reticulum of muscle cells.
     • Run Longitudinally along myofibril communicating with each other at HZone.
     • SR regulates calcium storage and releases Ca on demand when muscle fiber is stimulated to contract.
   • Terminal Cisterns: form larger cross channels at the A band-I band junction. Always in pairs.