GB2 REVIEWER

• Muscular and skeletal systems


  • Provide support to the body
  • Allow for a wide range of movement
• Hydrostatic skeleton


  A skeleton formed by a fluid-filled compartment within the body, called the COELOM
• Exoskeleton


  An external skeleton that consists of hard encasement on the surface of an organism
• Endoskeleton


  Consists of hard, mineralized structures located within the soft tissue of organisms
• Example of primitive endoskeletal structure

  • Spicules of sponges
• Human skeleton


  • 206 bones in the adult
  • Provides support to the body
  • Stores minerals and lipids
  • Produces blood cells
  • Protects internal organs
  • Allows for movement
• Muscle


  Muscle cells are specialized for contraction
• Types of muscle tissue

  • Skeletal muscle
  • Smooth muscle
  • Cardiac muscle

  
• Smooth muscle


  Found in walls of hollow organs such as stomach, intestines, blood vessels, uterus, etc.
• Cardiac muscle


  Found only in heart and are involuntary
• Skeletal muscle


  Voluntary muscles and is long and cylindrical in appearance

  
• Skeletal muscle fiber


  • Each skeletal muscle fiber is a skeletal muscle cell
  • Incredibly large, with diameters of up to 100 µm and lengths of up to 30 cm

  
• Sarcolemma


  • The plasma membrane of a skeletal muscle fiber
  • Site of action potential conduction, which triggers muscle contraction
• Myofibrils


  • Long cylindrical structures that lie parallel to the muscle fiber
  • Run the entire length of the muscle fiber
  • Approximately 1.2 µm in diameter, hundreds to thousands can be found inside one muscle fiber
  • Attach to the sarcolemma at their ends, so that as myofibrils shorten, the entire muscle cell contracts

  
• Sarcoplasm


  The cytoplasm of a muscle fiber
• Striations


  The striated appearance of skeletal muscle tissue is a result of repeating bands of the proteins actin and myosin that are present along the length of myofibrils

  
• Z line or Z disc


  The dense line running vertically through the middle of each I band
• Sarcomere


  • Region from one Z line to the next Z line and contains one entire A band and two halves of an I band, one on either side of the A band
  • The Z line mark the border of units called sarcomeres, which are the functional units of skeletal muscle
  • A myofibril is composed of many sarcomeres running along its length

  
• Myofilaments


  • Smaller structures
  • Two main types: thick filaments and thin filaments
• Thick filaments (myosin)


  Occur only in the A band of myofibril
• Thin filaments (actin)


  • Attach to a protein in the Z line called alpha-actinin and occur across the entire length of the I band and partway into the A band
  • The primary component is the actin protein
  • Two other components are tropomyosin and troponin
• Tropomyosin


  Strands of tropomyosin block the binding sites and prevent actin-myosin interactions when the muscles are at rest
• Troponin


  Consists of three globular subunits: one subunits binds to tropomyosin, one subunit binds to actin, and one subunits binds Ca2+ ions
• Herbivores


  • Vertebrates - deer, koalas
  • Invertebrates - caterpillars
  • Frugivores - fruit-eaters
  • Granivores - seed eaters
  • Nectivores - nectar feeders
  • Folivores - leaf eaters
• Carnivores

  • Obligate Carnivores - rely entirely on animal flesh to obtain their nutrients; lions and cheetahs
  • Facultative Carnivores - eat non-animal food
• Omnivores


  Eat both plant- and animal-derived food; chickens