Chapter 07 - Muscular

• Types of Muscles


  • Skeletal
  • Cardiac
  • Smooth
• Skeletal muscles


  • Attached to bones
  • Striated
  • Voluntarily controlled
• Cardiac muscles


  • Located in the heart
  • Striated
  • Involuntarily controlled
• Smooth muscles


  • Located in blood vessels, hollow organs
  • Non-striated
  • Involuntarily controlled
• Functions of the Muscular System

  • Movement
  • Maintain posture
  • Respiration
  • Production of body heat
  • Communication
  • Heart beat
  • Contraction of organs and vessels
• Contractility


  The ability of muscle to shorten forcefully, or contract
• Excitability


  The capacity of muscle to respond to a stimulus
• Extensibility


  The ability to be stretched beyond its normal resting length and still be able to contract
• Elasticity


  The ability of the muscle to recoil to its original resting length after it has been stretched
• Skeletal muscle, or striated muscle, with its associated connective tissue, constitutes approximately 40% of body weight
• Skeletal muscle is so named because many of the muscles are attached to the skeletal system
• Some skeletal muscles attach to the skin or connective tissue sheets
• Skeletal muscle is also called striated muscle because transverse bands, or striations, can be seen in the muscle under the microscope
• Individual skeletal muscles, such as the biceps brachii, are complete organs, as a result of being comprised of several tissues: muscle, nerve, and connective tissue
• Epimysium


  A connective tissue sheath that surrounds each skeletal muscle
• Fascicle


  A group of muscle cells within a skeletal muscle
• Perimysium


  A connective tissue covering that surrounds each fascicle
• Endomysium


  A connective tissue covering that surrounds each skeletal muscle cell (fiber)
• Muscle fiber


  A single cylindrical cell, with several nuclei located at its periphery
• Muscle fibers range in length 1 cm to 30 cm and are generally 0.15 mm in diameter
• Skeletal muscle fibers contain several nuclei that are located at the periphery of the fiber
• Sarcolemma


  The cell membrane of a muscle fiber
• Transverse tubules (T tubules)


  Tubelike inward folds of the sarcolemma that extend into the center of the muscle fiber
• Terminal cisternae


  Enlarged portions of the smooth endoplasmic reticulum associated with the T tubules
• Muscle triad


  The T tubules connected to the terminal cisternae
• Sarcoplasmic reticulum


  The smooth endoplasmic reticulum in muscle fibers that has a high concentration of Ca2+
• Sarcoplasm


  The cytoplasm of a muscle fiber
• Myofibrils


  Bundles of protein filaments in the sarcoplasm
• Myofilaments


  The actin and myosin filaments that make up the myofibrils
• Sarcomere


  The basic structural and functional unit of a skeletal muscle, capable of contracting
• Z disks


  Protein fibers that anchor the actin myofilaments and separate one sarcomere from the next
• I bands


  Light-staining bands consisting only of actin myofilaments
• A bands


  Dark-staining bands extending the length of the myosin myofilaments
• Actin myofilaments


  Made up of actin, troponin, and tropomyosin
• Troponin


  Molecules with binding sites for Ca2+
• Tropomyosin


  Filaments that block the myosin myofilament binding sites on the actin myofilaments
• Myosin myofilaments


  Also called thick myofilaments, resemble bundles of tiny golf clubs with ATP binding sites, ATPase, and attachment spots for actin
• Resting membrane potential


  The electrical charge difference across the cell membrane of an unstimulated cell
• Action potential


  A rapid change in charge across the cell membrane
• Depolarization


  When the inside of the cell membrane becomes more positively charged than the outside of the cell membrane