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Muscular Contractions

Muscular Contractions. Contracting and Relaxing Skeletal Muscle. Anatomy of a Muscle Fiber (Cell). Sarcolemma Myofibril Sarcomere Z line. Anatomy of a Sarcomere. Actin Myosin. Contraction Overview. Lovely artwork courtesy of David Goodsell and the RCSB Protein Data Bank.

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Muscular Contractions

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  1. Muscular Contractions Contracting and Relaxing Skeletal Muscle

  2. Anatomy of a Muscle Fiber (Cell) • Sarcolemma • Myofibril • Sarcomere • Z line

  3. Anatomy of a Sarcomere • Actin • Myosin

  4. Contraction Overview Lovely artwork courtesy of David Goodsell and the RCSB Protein Data Bank

  5. Steps of a Muscle Contraction • Nerve causes release of acetylcholine (ACh)

  6. Steps of a Muscle Contraction • Reception of ACh causes an action potential (electrical nerve signal) in muscle cell

  7. Steps of a Muscle Contraction • Action potential causes release of calcium in muscle cell • Meanwhile…

  8. Steps of a Muscle Contraction • Calcium binds, forming troponin complex and revealing myosin binding sites.

  9. Steps of a Muscle Contraction • Sliding filament theory

  10. Contraction Overview Lovely artwork courtesy of David Goodsell and the RCSB Protein Data Bank

  11. Relaxation • Acetylcholinesterase breaks down Ach • Active transport prepares the muscle cell for future action potentials • Active transport removes free calcium from muscle cells • ATP breaks actin-myosin linkage

  12. Relaxation

  13. Interference • Botox & botulism – block acetylcholine release • Rigor mortis – can’t keep calcium out of cells so muscles contract, lack of ATP prevents myosin from releasing actin

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