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Extra credit − − How are we on bones? − − opportunities on webpage see me for details, questions axial skeleton appendicular skeleton Today − − Ch.6 Muscular System Intro Guest Lecturer-Rob Chapter 6 The Muscular System Muscle Main function? 3 types − skeletal − cardiac − smooth Skeletal Muscle skeletal, striated, voluntary responsible for the majority of the tissue in skeletal muscles What other tissues are found in skeletal muscle? Skeletal Muscle Functions − Movement − Maintain posture and body movement − Stabilizes joints, support visceral organs − Maintain body temperature − Can you think of any special actions of skeletal muscles? Skeletal muscle is bundled in layers of connective tissue epimysium − perimysium − peri = around, about endomysium − epi = upon, over endo = internal muscle fiber = muscle cell myofibril = organelle Do skeletal muscle cells have the same basic cellular structures? Yes! But they have different names Sarcolemma: plasma membrane Sarcoplasm: cytoplasm New to skeletal muscle cells Sarcoplasmic reticulum − specialized smooth ER, stores and releases calcium ions Inside a muscle fiber (cell) note the myofibrils Myofibrils Contractile portion of a muscle fiber Consist of thick and thin filaments These filaments are responsible for the banding pattern: dark and light bands Made up of chains of tiny units known as sarcomeres Sarcomere smallest contractile unit of a muscle fiber Let’s review what we have covered….levels of organization Myofibrils are made of thick & thin filaments Thick filaments − myosin − ATPase enzymes − split ATP to generate power for contraction A band dark Myofibrils: thick filaments projections − myosin heads − form cross bridges linking thick and thin filaments Myofibrils: thin filaments thin filaments − actin − anchored to Z disc − I band light Now that you know the structure of a muscle fiber… Can you propose what happens when a contraction occurs? What other components are required for a contraction? Where will these other components come from? Notice during contraction the sarcomere shortens.
