BIO 118 Test #2 Notes - Muscles and movement 52 What are...

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Muscles and movement 52. What are the characteristics of smooth muscle, cardiac muscle, and skeletal muscle? Where are these muscle types found in the body? - Smooth muscle: not voluntary, not striated, dividing, and can be found surrounding hollow structures (ex: blood vessel, stomach); moves food, urine and reproductive tract secretions; controls diameter of respiratory passageways; regulates diameter of blood vessels - Cardiac muscle: not voluntary, striated, not dividing, located in heart; circulates blood and maintains blood (hydrostatic) pressure - Skeletal: voluntary, striated, not dividing, connected to skeleton; moves or stabilizes the position of the skeleton; guards entrances and exits to the digestive, respiratory, and urinary tracts; generates heat; protects internal organs 53. What is a muscle cell specialized to do? - it is specialized for contraction 54. What is striation? - a series of bands in muscles to appear marked 55. Describe the overall structure of skeletal muscle. - A skeletal muscle contains connective tissues, blood vessels, nerves, and skeletal muscle tissue. Three layers of connective tissue are part of each muscle: the epimysium, the perimysium, and the endomysium. - Surrounding the entire muscle is the epimysium, a layer of collagen fibers that separates the muscle from surrounding tissues and organs.
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- the connective tissue fibers of the perimysium divide the skeletal muscle into compartments, each containing a bundle of muscle fibers called a fascicle - within a fascicle, the endomysium surrounds each skeletal muscle fiber and ties adjacent muscle fibers together - they all come together to form either a bundle known as a tendon, or a broad sheet called an aponeurosis at the end of each muscle (this is how they attach to the bone) 56. Why are skeletal muscle cells multinucleated? - This occurs in skeletal muscle in order to permit the simultaneous contraction of all the actomyosin contractile units along the length of the fiber: if they were many separate cells, they would have to communicate with each other, which would slow the contractile "signal", and result in slower contraction. 57. Define the following terms, and understand their relationship to each other: myofibril, sarcomere, myofilaments, actin, myosin, troponin, tropomyosin. - myofibril: bundles of thick and thin myofilaments (protein filaments consisting primarily of the proteins actin and myosin) - Sarcomere: the smallest functional unit of the muscle fiber; interactions between the thick and thin filaments of sarcomeres are responsible for muscle contraction - Myofilaments: protein filaments consisting primarily of the proteins actin and myosin - Actin: protein component of microfilaments; form thin filaments in skeletal muscles and produce contractions of all muscle through interaction with thick (myosin) filaments
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- Myosin: protein component of microfilaments - Troponin: a protein on thin filaments that masks the active sites in the absence of free calcium ions
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