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Muscle Contractions

Muscle Contractions. Sliding Filament Theory. Goal:. I will be able to explain the Sliding Filament Theory. . Skeletal Muscle. Similar to Fig. 3.4 on page 36. Sliding Filament Theory muscle contraction. Muscle Fibers.

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Muscle Contractions

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  1. Muscle Contractions Sliding Filament Theory

  2. Goal: • I will be able to explain the Sliding Filament Theory.

  3. Skeletal Muscle

  4. Similar to Fig. 3.4 on page 36

  5. Sliding Filament Theory • muscle contraction

  6. Muscle Fibers • Muscle fibers contain cylindrical bundles called myofibrilswhich extend from one end of the muscle to the other. • Each myofibril is composed of thick and thin filaments arranged in a repeating pattern. • One unit of repeating pattern in known as a sarcomere.

  7. The thick filaments are composed almost entirely of a contractile protein myosin. • The thin filaments contain the contractile protein actin as well as two other proteins – troponin and tropomyosin.

  8. Sliding Filament Theory • A message is released from the central nervous system. • The message travels from neuron to neuron until it reaches the specific motor unit. • Acetylcholine (ACh) is released from the axon terminal of the motor unit. • The ACh causes the release of Ca2+ into the cytoplasm of the muscle fiber.

  9. The calcium ions attach to troponin sites on the actin molecule which causes the molecule to shift. • The myosin binding sites, which are normally guarded by tropomyosin, are exposed allowing myosin to bond with actin. • The bonding is known as a cross-bridge and allows for an overlap of the filaments and thus a contraction. • This entire process does require energy in the form of ATP.

  10. Work • Find the diagram of the structure of a skeletal muscle. Identify and colour the sarcomere, actin, myosin, and cross bridges. • Complete the Muscle Contraction and Sliding Filament Theory sheet from yesterday. • Explain at the molecular level how you are able to brush your teeth. Use scientific terms in your answer.

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