Final Exam Study Guide Non Cumulative Portion Lesson 20 1 What are the six functions of skeletal muscle tissue Support soft tissues line abdominal wall and pelvic cavity a Produce skeletal movement Voluntary b Maintain posture and body position c d Guard entrances and exits ex Sphincters in alimentary canal urethra e Maintain body temperature ex Contractions produce heat shivering f Store nutrient reserves breaks down muscle protein when needed 2 How are skeletal muscles organized What are connective tissue layers that are found covering muscles What can be found in each layer blood vessels nerves Organization o Muscle tissue muscle cells or fibers A muscle cell is also referred to as a muscle fiber o Associated with the tissue are Connective tissues Nerves Blood vessels Layers o Epimysium from surrounding tissues Exterior collagen layer connected to deep fascia separates muscle o Perimysium Surrounds muscle fiber bundles forms fascicles Contains blood vessel and nerve supply to fascicles o Endomysium Surrounds individual muscle cells muscle fibers Contains capillaries and nerve fibers contacting muscle cells Contains myosatellite cells stem cells that can repair some damage minimal repair ability Tendon Epimysium Blood vessels and nerves Endomysium Perimysium 3 What are the structural components of a muscle fiber What are myofibrils What are myofilaments Structural Components of muscle fiber o The Sarcolemma The cell membrane of a muscle fiber cell Surrounds the sarcoplasm cytoplasm of muscle fiber A change in transmembrane potential begins contractions o Transverse tubules T tubules invagination of the sarcolemma Have same properties as sarcolemma Transmit action potential through cell Allow entire muscle fiber to contract simultaneously o Myofibrils Lengthwise subdivisions within muscle fiber Made up of bundles of protein filaments myofilaments Myofilaments are responsible for muscle contraction Types of myofilaments o Thin filaments Made of the protein actin o Thick filaments Made of the protein myosin o The Sarcoplasmic Reticulum SR Similar in structure to smooth endoplasmic reticulum A membranous structure surrounding each myofibril Forms chambers terminal cisternae attached to T tubules Helps transmit action potential to myofibril Is formed by one T tubule and two terminal cisternae Triad Cisternae functions to o Concentrate Ca2 via ion pumps Ca2 pumps use ATP to actively pump Ca2 into the SR from the sarcoplasm o When stimulated by an action potential the cisternae release Ca2 into sarcomeres to begin muscle contraction Myofibril Sarcolemma Nuclei Sarcoplasm MUSCLE FIBER Mitochondria Sarcolemma Myofibril Thin filament Thick filament TriadSarcoplasmic reticulum T tubules Terminal cisterna Sarcolemma Sarcoplasm Myofibrils 4 What are the differences between thick and thin filaments How are they organized in muscle fibers How are they arranged in a sarcomere Myofilaments Protein filaments responsible for muscle contraction o Thick filaments Made of the protein myosin Helps keep thick and thin filaments aligned and restores resting Contain about 300 twisted myosin subunits Contain titin strands that recoil after stretching sarcomere length after contration The myosin molecule consists of Tail Binds to other myosin molecules Head Made of two globular protein subunits Can extend and bind to myosin binding site of the nearest thin filament o Thin Filaments Made of the protein actin F actin filamentous actin Two twisted rows of globular G actin The active sites on G actin strands bind to myosin Tropomyosin double strand regulatory protein Prevents actin myosin interaction Troponin A globular regulatory protein Binds tropomyosin to G actin Controlled by Ca2 Binding of Ca2 causes a change in troponin o Arrangement in Sarcomere The A Band M line The center of the A band At midline of sarcomere The H band The area around the M line Has thick filaments but no thin filaments Zone of overlap The densest darkest area on a light micrograph Where thick and thin filaments overlap The I Band Z lines The centers of the I bands At two ends of sarcomere Titin Are strands of protein Reach from tips of thick filaments to the Z line Stabilize the filaments Sarcomere I band A band Contains Thick filaments Thin filaments Z line Titin Z line M line H band 5 What are the zones and lines in a myofibril What are the different regulatory and structural proteins found in a muscle fiber What are their functions Lines and Zones o The A Band M line The center of the A band At midline of sarcomere o The H band The area around the M line Has thick filaments but no thin filaments o Zone of overlap The densest darkest area on a light micrograph Where thick and thin filaments overlap o The I Band Z lines The centers of the I bands At two ends of sarcomere Titin Are strands of protein Reach from tips of thick filaments to the Z line Stabilize the filaments Regulatory and structural Proteins in muscle fiber o F actin filamentous actin Two twisted rows of globular G actin The active sites on G actin strands bind to myosin o Tropomyosin double strand regulatory protein Prevents actin myosin interaction o Troponin A globular regulatory protein Binds tropomyosin to G actin Controlled by Ca2 Binding of Ca2 causes a change in troponin 6 How are T tubules related to the sarcolemma Why are they important to a muscle fiber What is a triad and why is it important Transverse tubules T tubules invagination of the sarcolemma o Have same properties as sarcolemma o Transmit action potential through cell o Allow entire muscle fiber to contract simultaneously Triad formed by one T tubule and two terminal cisternae o Cisternae functions to Concentrate Ca2 via ion pumps Ca2 pumps use ATP to actively pump Ca2 into the Sarcoplasmic reticulum from the sarcoplasm When stimulated by an action potential the cisternae release Ca2 into sarcomeres to begin muscle contraction 7 What is the function of calcium in muscle contraction Where is it normally concentrated in a o Ca2 binds to receptor on troponin molecule o Troponin tropomyosin complex changes o Tropomyosin strand shifts in position so it no longer covers the active site of the muscle fiber How is it concentrated there During the initiation of a contraction F actin strand o Exposes active site of actin Calcium concentration o Terminal Cisternae Concentrate Ca2 via ion pumps Ca2 pumps use ATP to actively pump Ca2 into the SR from the sarcoplasm When stimulated by an action potential
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