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Activation of Contraction in Smooth vs. Skeletal Muscle

How are the differences in smooth and skeletal muscle contraction related to function? Muscle tissue is used in movement. There are three primary types of muscle in vertebrates: cardiac muscle, smooth muscle and skeletal muscle, which is also known as striated muscle. Skeletal muscle is involved in voluntary movement. As its name implies, skeletal muscle, is associated with the skeleton. Many of the body’s organs are composed of smooth muscle. Smooth muscle is generally not under voluntary control. Skeletal muscle is required for rapid and relatively large movements. Therefore skeletal muscle cells are frequently organized into long, slender bundles that are called muscles. In contrast smooth muscles are usually organized into thin sheets. These sheets are not well designed for rapid movement but can contract to control movement through organs.

View the animation below, then complete the quiz to test your knowledge of the concept.






1The sequence for smooth muscle contraction is...
A)increased cytosolic calcium, which binds to troponin, complex binds with myosin light-chain kinase, which uses ATP to phosphorylate myosin cross-bridges, which bind to actin filaments, resulting in contraction.
B)increased cytosolic calcium, which binds to calmodulin in cytosol, which binds with myosin cross-bridges, resulting in contraction.
C)increased cytosolic calcium, which binds to calmodulin in cytosol, which moves tropomyosin from blocking active sites on actin filament, which binds with myosin cross-bridges, resulting in contraction.
D)increased cytosolic calcium, which binds to troponin, which moves tropomyosin from blocking active sites on actin filament, which binds with myosin cross-bridges, resulting in contraction.
E)increased cytosolic calcium, which binds to calmodulin in cytosol, complex binds with myosin light-chain kinase, which uses ATP to phosphorylate myosin cross-bridges, which bind to actin filaments, resulting in contraction.



2The sequence for skeletal muscle contraction is...
A)increased cytosolic calcium, which binds to troponin, complex binds with myosin light-chain kinase, which uses ATP to phosphorylate myosin cross-bridges, which bind to actin filaments, resulting in contraction.
B)increased cytosolic calcium, which binds to calmodulin in cytosol, which binds with myosin cross-bridges, resulting in contraction.
C)increased cytosolic calcium, which binds to calmodulin in cytosol, which moves tropomyosin from blocking active sites on actin filament, which binds with myosin cross-bridges, resulting in contraction.
D)increased cytosolic calcium, which binds to troponin, which moves tropomyosin from blocking active sites on actin filament, which binds with myosin cross-bridges, resulting in contraction.
E)increased cytosolic calcium, which binds to calmodulin in cytosol, complex binds with myosin light-chain kinase, which uses ATP to phosphorylate myosin cross-bridges, which bind to actin filaments, resulting in contraction.



3Which of the following statements is true concerning calcium ions?
A)in smooth muscle it binds with calmodulin.
B)in skeletal muscle it binds with calmodulin.
C)in smooth muscle it binds with troponin.
D)in skeletal muscle it binds with tropomyosin.
E)in smooth muscle it binds with myosin light-chain kinase.



4Smooth muscle and skeletal muscle fibers both have their contractions triggered by calcium ions.
A)True
B)False



5Both smooth muscle contractions and skeletal muscle contractions involve thin (actin) filaments sliding over the thick (myosin) filaments.
A)True
B)False







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