Muscle Types PDF

MUSCLE TYPES Skeletal Cardiac Smooth Striations Striated Striated Non-striated Control Voluntary Involuntary Involuntary Innervation Somatic Autonomic Autonomic Function Moveme...

MUSCLE TYPES Skeletal Cardiac Smooth Striations Striated Striated Non-striated Control Voluntary Involuntary Involuntary Innervation Somatic Autonomic Autonomic Function Movement Pumping of blood According to site Site Attached to bone Heart GIT - blood vessels 1  MUSCLE PROTEINS  Structure of striated muscle:  Striated muscle is composed of multinucleated cell called muscle fiber.  In the sarcoplasm of muscle fiber there are many parallel myofibrils.  When myofibrils are examined by electron microscopy, alternating dark band (A band) (100 A° in diameter) and light band (I band) (50 A°) can be observed.  A-band has lighter central H-zone (has no actin filaments) (M-line in the center of H).  Myofibrils contain two types of longitudinal fiber, thick filaments (myosin) and thin filaments (actin, tropomyosin and troponin). 2  A. CONTRACTILE PROTEINS 1. Myosin:  Myosin is a complex protein (MW = 480,000).  Composed of 6 polypeptide chains (2 heavy and 4 light).  The 2 heavy chains folded around each other as double helix forming long tail and arms.  While the terminal part of heavy chains combines with the 4 light chains forming 2 globular heads.  Head contains 2 sites: Actin-binding site and ATP hydrolysis site.  Cross bridges arise from the head at 2 hinges to bind to the actin (one between the arm and tail and the other between the arm and heads).  There are 2 types of Myosin:  Type 1 contain single head without tail and not present in skeletal muscle.  Type 2 contain 2 heads and tail and present in skeletal muscle. 3 2. Actin:  It is a small globular protein (MW = 42,000).  The globules are attached to each other to form filaments arranged in two chains as long double helix. B. REGULATORY PROTEINS 1. Tropomyosin (inhibitory protein):  It is a long filament located between the 2 chains of actin.  It covers the active sites of actin which combine to myosin.  It inhibits binding of actin to myosin during rest. 2. Troponin:  Troponin C:  Binds to Calcium ions.  Troponin T:  Binds to Tropomyosin.  Troponin I:  Inhibit binding of actin to myosin. 4  C. OTHER PROTEINS 1. Myoglobin: O2 storage protein 2. Elastic proteins. 3. Actinin: binds actin to the Z lines. 4. Titin: is a large protein which connects the Z line to the M line. 5. Dystrophin-glycoprotein complex:  It is a large protein called dystrophin and other called dystroglycan form rods that connects the actin filaments to laminin in the extracellular.  This complex provides structural support and strength to the muscle fibre. 5 SARCO TUBULAR SYSTEM 6 MUSCLE CONTRACTION 7 Tilting ATP Binding Detachment 8 9