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Topic 11.2 Movement

Topic 11.2 Movement. Bone and Muscle. Bones . Bones and muscles work together to move the body Bone and exoskeleton provide framework. Skeletal muscle are antagonistic. Work in pairs When one relaxes the other contracts Example, biceps and triceps. Elbow Joint.

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Topic 11.2 Movement

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  1. Topic 11.2 Movement Bone and Muscle

  2. Bones • Bones and muscles work together to move the body • Bone and exoskeleton provide framework

  3. Skeletal muscle are antagonistic • Work in pairs • When one relaxes the other contracts • Example, biceps and triceps

  4. Elbow Joint • Joints are where two bones meet • Joints allow movement in different directions • Synovial joints: have synovial fluid to prevent friction • Elbow and knee are hinged synovial joint • Ball and socket joints (shoulder and hip) • Pivot joint (head) • Gliding joint (wrist)

  5. Elbow joint

  6. Parts & functions

  7. Muscle Types • Three types of muscle tissue • Skeletal or striated • Cardiac • smooth

  8. Skeletal muscle • Composed of myofibrils (actin & myosin) • Arranged in unique ways for distinct functions • Sliding over each other • Basic unit of a muscle contraction is called a sarcomere

  9. Each muscle cell can contain thousands of sarcomeres • Each sarcomere is made of a myofibril • Myofibril contains actin and myosin • Actin is the thin filament • Myosin is the thick filament

  10. Stacked myofibrils are found within each cell surrounded by the muscle cell membrane called the sarcolemma • Contains T tubules (transverse) • Reach deep into the cell • Increase surface area of sarcolemma

  11. Skeletal muscle can be very long so it is multinucleated • Also contain a special endoplasmic reticulum called the sarcoplasmic reticulum • Stores and releases calcium as needed to initiate a muscle contraction • Packed with mitochondria for energy

  12. Sarcomere • Functional unit of muscle cells • Composed of many repeating sarcomeres • Composed of sliding filaments

  13. Contraction of skeletal Muscle • Initiated by and action potential from the nervous system • Steps are as follows: • 1. action potential arrives at terminal button releasing a neurotransmitter (acetylcholine) • 2. Neurotransmitter released into synapse • 3. Neurotransmitter is attached to receptors on sodium gated channels on sarcolemma (depolarization)

  14. 4. Action potential spreads through T-tubules of sarcolemma releasing calcium from sarcoplasmic reticulum • 5. calcium attached to troponin (protein) causes tropomyosin to shift, exposing myosin binding sites • 6. each myosin head binds an ATP and splits the ATP into ADP + Pi (inorganic phosphate) causing the myosin head to bend outwards • 7. Each myosin head forms a cross-bridge with actin & releases the Pi. Release of Pi causes myosin heads to bend inward and slide the actin over the myosin (shortening sarcomere)

  15. 8. Each myosin head binds a new ATP to break the cross-bridge • 9. The cycle repeats until no more action potentials are sent and calcium is pumped back into the sarcoplasmic reticulum

  16. Sliding filament Theory

  17. Electron Micrograph of Skeletal Muscle

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