MUSCULAR SYSTEM

MUSCULAR SYSTEM

FUNCTIONS

  • structural
  • Protection
    • Ex. RECTUS ABDOMINIS (protects internal organs of trunk)
  • movement/restriction
  • heat production (ex. shivering)
  • effects on other systems

SKELETAL MUSCLE

  • attached to bone/cartilage
  • Striated
    • due to repeating units of actin and myosin - proteins; their interaction allows muscles to contract and move which is known as the sliding filament model)
  • voluntary
  • Components:
    • MYOFILAMENTS: myosin and actin filaments
    • SARCOMERE (contractile units that enable movement)
      • sarcomere is made up of myofilaments
    • MYOFIBRIL (multiple repeating sarcomeres)
    • MUSCLE FIBER (bundles of myofibrils; individual Cells)
    • FASCICULUS (multiple muscle fibers bundled tgt)
    • SKELETAL MUSCLE (made up of bundles of fasciculi)

SLIDING FILAMENT MODEL

  • interaction btw the short knobs of myosin and the filaments of actin
  • the interaction of the myofilaments inside the sarcomere will allow it to contract. when multiple sarcomere contract, they become smaller, and in doing so the entire muscle contracts as well, which allows them to move the bones/cartilage they are attached to

FISH MUSCULATURE

  • axial musculature (associated w vertebral column): MYOTOMES
    • characterized by a distinct folded pattern. this generates a greater force for a larger portion of the fish’s body (more energy efficient)
    • multiple myotomes work tgt to generate the force needed for swimming
    • separated by MYOSEPTA
  • appendicular: minimal (bc the appendicular muscles aren’t rlly used for swimming, mostly used for stabilizing)

TETRAPOD MUSCULATURE

  • axial: generally reduced, but specialized
    • used for functions like respiration (ex. muscles associated w ribs help breathing by expanding rib cage), support, etc
    • less for movement in later tetrapods
  • appendicular: very prominent (since they’re used for locomotion), more distinct muscles, attached to:
    • limbs
    • pelvic girdle
    • pectoral girdle - muscular sling - trapezius, rhomboideus, pectoralis, serratus ventralis (for trunk support & weight of the organism)

exception: salamanders