Muscle

Muscle

1. Types of muscle

   • Smooth muscle
     • single core
       • no striations
     • vascular tissue, walls of the digestive tract, organs that contain a lumen
       • tracts of the respiratory, urinary, and reproductive systems
         • also present in the eye
     • involuntary muscle
       • contraction relies on the presence of Ca++ ions
   • Striated muscles
     • Skeletal muscle
       • contract and cause movement
         • prevent excess movement of the bones and joints
           • maintaining skeletal stability and preventing skeletal structure damage or deformation
             • protect internal organs (particularly the abdominal organs)
               • contribute to the generation of heat
       • located throughout the body at the openings of internal tracts to control the movement of various substances
       • include the skeletal muscle fibers, blood vessels, nerve fibers, and connective tissue
         • Contain epimysium, perimysium, and endomysium
           • muscle fibers are organized into individual bundles (called fascicles)
             • The plasma membrane is called the sarcolemma
     • Cardiac muscle
       • only found in the heart, specifically the myocardium
       • coordinated contractions of cardiac muscle pump blood into the vessels of the circulatory system such as the aorta and pulmonary artery
         • is striated and organized into sarcomeres
           • usually contain only one nucleus, which is located in the central region of the cell.
             • contain many mitochondria
         • Cardiac muscle fibers cells also are extensively branched and are connected to one another at their ends by intercalated discs
           • involuntary contractions
             • blood pumping
             • rhythmic contraction
   • Keywords
     • Myofibers
       • The term for a muscle cell.
     • Myofibrils
       • The tube like organelle present in skeletal muscle and cardiac muscle that coordinates contraction of the cell.
     • Sarcomere
       • The basic functional unit of striated muscle that is composed of myofilaments.
     • Intercalated disc
       • A structure specific to cardiac muscle formed from gap junctions and desmosomes that allow cardiac muscle cells to contract in a coordinated fashion.
     • T tubules
       • Invaginations of the sarcolemma (cell membrane) into the cell that allows for the conduction of depolarization impulses from the outside of the cell to around the sarcomeres.