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How Animals Move

How Animals Move

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How Animals Move

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  1. How Animals Move Chapter 32

  2. Skeleton • A medium or structural element against which contractile cells can act • Three types • Hydrostatic • Exoskeleton • Endoskeleton exoskeleton

  3. Endoskeleton • All vertebrates have endoskeletons • Fins or limbs attach to skeleton at pectoral and pelvic girdles

  4. s clavicle scapula sternum humerus rib radius vertebral column ulna pelvic girdle femur patella tibia fibula Human Skeleton

  5. Functions of Bone • Interact with muscle to enable movement • Support and anchor muscles • Enclose and protect internal organs • Store calcium and phosphorus • Produce blood cells

  6. Long Bone Structure • Compact bone • Spongy bone • Central cavity contains yellow marrow

  7. Compact Bone Structure • Mature compact bone consists of many cylindrical Haversian systems

  8. Bone Marrow • Yellow marrow • Fills the cavities of adult long bones • Is largely fat • Red marrow • Occurs in spongy bone of some bones • Produces blood cells

  9. Long Bone Formation

  10. Bone Remodeling • In adults, bone building and bone breakdown continue constantly • Osteoblasts deposit bone • Osteoclasts secrete enzymes that degrade it • Remodeling adjusts bone strength and helps maintain blood calcium levels

  11. Bone Density • Exercise can increase bone density • Osteoporosis is a decrease in bone density • May occur when the action of osteoclasts outpaces that of osteoblasts • May also occur as a result of inability to absorb calcium

  12. Joints • Areas of contact or near contact between bones • Fibrous joints • Short connecting fibers join bones • Synovial joints • Move freely; ligaments connect bones • Cartilaginous joints • Straps of cartilage allow slight movement

  13. Skeletal Muscle • Bundles of striped muscle cells • Attaches to bone • Often work in opposition biceps triceps

  14. Tendons Attach Muscle to Bone muscle tendon bursae synovial cavity


  16. Skeletal Muscle Structure • A muscle is made up of muscle cells • A muscle fiber is a single muscle cell • Each fiber contains many myofibrils myofibril

  17. Sarcomere A myofibril is made up of thick and thin filaments arranged in sarcomeres sarcomere sarcomere sarcomere sarcomere Z band Z band Z band

  18. Muscle Microfilaments Thin filaments • Like two strands of pearls twisted together • Pearls are actin • Other proteins in grooves in filament Thick filaments • Composed of myosin • Each myosin molecule has tail and a double head

  19. Sliding-Filament Model Sarcomere shortens because the actin filaments are pulled inward, toward the sarcomere center

  20. Sliding-Filament Model • Myosin heads attach to actin filaments • Myosin heads tilt toward the sarcomere center, pulling actin with them

  21. Role of Calcium in Contraction • T tubules in the sarcoplasmic reticulum relay signal • Calcium ions are released

  22. Nervous System Controls Contraction • Signals from nervous system travel along spinal cord, down a motor neuron • Endings of motor neuron synapse on a muscle cell at a neuromuscular junction

  23. Contraction Requires Energy • Muscle cells require huge amounts of ATP energy to power contraction • The cells have only a very small store of ATP • Three pathways supply ATP to power muscle contraction

  24. ATP for Contraction

  25. Motor Unit • One neuron and all the muscle cells that form junctions with its endings • When a motor neuron is stimulated, all the muscle cells it supplies are activated to contract simultaneously • Each muscle consists of many motor units

  26. Twitches and Tetanus

  27. Muscle Tension • Mechanical force a contracting muscle exerts on an object • For a muscle to shorten, muscle tension must exceed the load that opposes it • The load may be the weight of an object or gravity’s pull on the muscle

  28. Two Main Types of Contraction • Isotonic contraction • Muscle visibly shortens; moves a load • Tension remains constant as the muscle changes length • Isometric contraction • Muscle does not change length • Tension is insufficient to move load

  29. Muscle Fatigue • An inability to maintain muscle tension • Occurs after a period of tetanic contraction • Different types of muscle show different fatigue patterns

  30. Muscular Dystrophies • A class of genetic disorders where muscles progressively weaken and degenerate • Duchenne muscular dystrophy is the most common among children • Myotonic muscular dystrophy is the most common among adults

  31. Aging Muscles • Over time, the number and size of muscle fibers decreases

  32. Clostridium • Clostridium botulinum – causes botulism, stopping the release of acetylcholine, a neurotransmitter that enables muscle contraction • Clostridium tetani – causes tetanus, blocking the neurotransmitters GABA and glycine, which leads to uninhibited muscle contraction