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Support and Locomotion

Support and Locomotion. Muscles. Muscles work by contracting: getting smaller in size Three types of muscles Skeletal (Striated, voluntary) Cardiac (Heart) Smooth (Involuntary). Skeletal Muscle. Called striated because of how it looks Responsible for voluntary actions

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Support and Locomotion

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  1. Support and Locomotion

  2. Muscles • Muscles work by contracting: getting smaller in size • Three types of muscles • Skeletal (Striated, voluntary) • Cardiac (Heart) • Smooth (Involuntary)

  3. Skeletal Muscle • Called striated because of how it looks • Responsible for voluntary actions • Human body has over 700 different skeletal muscles (this makes up ~35% to 45% of the total body weight!) • SkM contracts by having two proteins, actin and myosin, slide past each other

  4. Skeletal Muscle • The sarcomere is the functional unit of muscle contraction • Thin filaments consist of two strands of actin and one tropomyosin coiled about each other • Thick filaments consist of myosin molecules

  5. Actin (thin filament) and myosin (thick) slide past each other • Myosin has little “feet” called cross-bridges

  6. Skeletal Muscle • At rest, tropomyosin blocks the myosin binding sites on actin

  7. Skeletal Muscle • When Ca2+ binds to the troponin complex, a conformational change results in the movement of the tropomyosin- tropinin complex and exposure of actin’s myosin binding sites

  8. Skeletal Muscle • Using ATP, cross-bridges from myosin “grab” binding sites on actin and pull the filaments closer • This action occurs over and over until the muscle fiber is completely contracted

  9. Muscles are controlled by the Nervous System • Action potentials run along a neuron until they reach a synapse, where they release neurotransmitters (ACh) • Once at the muscle cells, the action potential releases Ca2+ from the sarcoplasmic reticulum • The Ca ions allow the proteins on the actin and myosin to bind, forming the cross-bridges

  10. Cardiac Muscles • Cardiac muscles are those that power the heart • Very similar to SkM, except CM is controlled by the SA node, not a motor neuron

  11. Smooth Muscles • SmM surround blood vessels and most hollow organs: uterus, bladders, GI tract • Most SmM contraction is slow and sustained, sometimes rhythmic (peristalsis)

  12. Smooth Muscles • SmM contraction can be initiated by stretching, hormones, or the nervous system • Most are involuntary, but some can be controlled (urinary bladder)

  13. ATP • Large amounts of ATP are required for muscle contraction AND relaxation • Breaks/reforms connections between actin and myosin • Powers pumps that return Ca2+ to the sarcoplasmic reticulum

  14. Rigor mortis • Stiffening of muscles after death • Muscles run out of ATP after death • Connection between actin and myosin cannot be broken – muscle remains contracted • After ~72 hours, relaxation occurs because of decomposition

  15. Skeletons • What do skeletons do? • Provide the framework for support of the body • Three basic types: • Hydrostatic Skeleton • Exoskeleton • Endoskeleton

  16. Hydrostatic Skeletons • fluid pressure provides support (Cnidarians, Annelids)

  17. Exoskeleton • Encase the bodies of Arthropods (insects, crustaceans, and arachnids) • Made of proteins, chitin, or are calcareous • Thin exoskeleton where the animal needs to bend or move

  18. Crustacea, Molluska, and Insecta

  19. Endoskeleton • Found in Echinoderms, Chordates, and Sponges • Serve several functions for vertebrates: • Supports body and protects internal organs • Used as muscle attachment sites to allow locomotion

  20. Produce blood parts (RBC’s, WBC’s, and platelets • Serve as storage sites for Calcium and Phosphorus • Some even aid in sensory transduction (hammer, anvil, and stirrup of the middle ear)

  21. Cartilage • Consists of chondrocytes embedded in a collagen/elastin matrix • Located at ends of long bones and between vertebrae • Functions as shock absorber

  22. Bones • Compact bone provides strength and rigidity as well as attachment sites for muscles • Spongy bone is very porous; site where blood cells are produced (bone marrow)

  23. How does the body move? • Muscles work in antagonistic pairs • One always extends (bends out) while the other always flexes (bends in)

  24. How does the body move? • A muscle attaching two bones is attached to one fairly immovable bone (origin) and one that moves (insertion) • Tendons connect muscle to bone • Ligaments connect bone to bone

  25. Joints are where two bones meet • Three basic types of joints: • Fixed: Skull • Hinge: Elbows and knees • Ball-and-Socket: Shoulders and hips

  26. Arthritis (joint inflammation) • Osteoarthritis (“wear-and-tear” arthritis) • Cartilage covering the ends of bones slowly wears away, causing stiffness and soreness • Rheumatoid arthritis • Autoimmune disease in which the body’s immune system attacks the synovial membranes

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