Lecture 21 Muscle

Lecture 21 Muscle - UNIT 4: PHYSIOLOGY AND SPECIALIZED...

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UNIT 4: PHYSIOLOGY AND SPECIALIZED CELLS In this section we will look at familiar physiological systems and examine how they work by learning about the specialized cells that lie at the core of each system. We’ll start with muscle by looking at the mechanics and regulation of the basic unit of muscle contraction—the sarcomere.
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Bundle of muscle fibers Muscle Single muscle fiber (cell) Nuclei Z lines Plasma membrane Myofibril Sarcomere Muscle, like many biological systems has a hierarchical organization: muscles consist of bundles of muscle fibers, Each fiber consists of a bundle of myofibrils. And each myofibril consists of a series of sarcomeres lying end-to- end. We can understand the basics of muscle contraction by examining a single sarcomere.
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When a muscle contracts its sarcomeres shorten which is due to myosin pulling the actin filaments toward the center of the sarcomere. This is called a “sliding filament” mechanism. . 0.5 μ m Z H A Sarcomere
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This cartoon shows how the main components are organized: Two sets of antiparallel actin filaments interact with one set of bipolar myosin filaments
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Thin filaments are composed of the protein actin and are found in nearly all types of cells
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17_40_Myosin_II.jpg
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Lecture 21 Muscle - UNIT 4: PHYSIOLOGY AND SPECIALIZED...

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