function, location, and structure of muscles

• Three Types of Muscle Tissue

  • Skeletal muscle tissue
  • Cardiac muscle tissue
  • Smooth muscle tissue

  
• Skeletal muscle tissue


  • Attached to bones and skin
  • Striated
  • Multi-nucleated
  • Voluntary (i.e., conscious control)
  • Powerful

  
• Cardiac muscle tissue


  • Only in the heart
  • Striated
  • Single nucleated
  • Involuntary
  • Autorhythmic
• Smooth muscle tissue


  • In the walls of hollow organs, e.g., stomach, urinary bladder, and airways
  • Not striated
  • Involuntary
  • Single nucleated
• Special Characteristics of Muscle Tissue

  • Excitability (responsiveness or irritability): ability to receive and respond to stimuli
  • Contractility: ability to shorten when stimulated
  • Extensibility: ability to be stretched
  • Elasticity: ability to recoil to resting length
• Muscle Functions


  • Movement of bones or fluids (e.g., blood)
  • Maintaining posture and body position
  • Stabilizing joints
  • Heat generation (especially skeletal muscle)
• Skeletal Muscle


  • Each muscle is served by one artery, one nerve, and one or more veins
• Connective tissue sheaths of skeletal muscle

  • Epimysium: dense regular connective tissue surrounding entire muscle
  • Perimysium: fibrous connective tissue surrounding fascicles (groups of muscle fibers)
  • Endomysium: fine areolar connective tissue surrounding each muscle fiber

  
• Skeletal Muscle: Attachments


  • Directly — epimysium of muscle is fused to the periosteum of bone or perichondrium of cartilage
  • Indirectly — connective tissue wrappings extend beyond the muscle as a ropelike tendon or sheetlike aponeurosis

  
• Microscopic Anatomy of a Skeletal Muscle Fiber

  • Cylindrical cell, up to 30 cm long
  • Multiple peripheral nuclei
  • Many mitochondria
  • Glycosomes for glycogen storage
  • Myoglobin for O2 storage
  • Also contain myofibrils, sarcoplasmic reticulum, and T tubules

  
• Cardiac Muscle is found only in the heart.
• Skeletal Muscle is attached to bones by tendons.
• Muscles are made up of muscle fibers.
• Z discs are located at the edges of the A bands where actin filaments overlap with adjacent myofibrils.
• Acetylcholine binds with receptors on motor end plates, causing depolarization of the sarcolemma and propagation of action potentials along transverse tubules into the interior of the muscle cells.
• T-tubules are invaginations of the sarcolemma into the center of the muscle fiber.
• The sarcolemma is the plasma membrane that surrounds the muscle fiber.
• Muscles contract when stimulated by nerves that release acetylcholine at neuromuscular junctions.