Clicker questions Clicker channel 70 Response Ware session ID psio201 For a person sitting normally in a chair with feet flat on the floor which of the following statements is correct 99 A thigh and leg are extended B thigh and leg are flexed C thigh is extended leg is flexed D thigh is flexed leg is extended 0 A 0 B C 1 D For a second class lever which of the following statements is correct A the effort is between the fulcrum and the load 91 B the fulcrum is between the load and the effort C the load is between the effort and the fulcrum 2 A 7 B C Lecture 17 Tissue and Cellular Organization of Muscle Claudia Stanescu Ph D Office hours Tuesday and Thursday 1 2pm in Gittings 108 or by appointment Objectives pp 291 301 sec 10 1 10 2 1 Describe the organization of muscle and the connective tissues surrounding each structure 2 Diagram and label the major structural and contractile elements of a muscle fiber and describe the function of each element 3 Diagram and label the major contractile and regulatory elements of the sarcomere 4 Diagram and label the thin and thick filaments including all of the proteins that make up each myofilament 5 Give a general description of the sliding filament mechanism Structural Organization of Skeletal Muscle Not shown in figure Groups of muscles covered by Deep Fascia Muscle covered by Epimysium Fascicle covered by Perimysium Muscle fiber covered by Endomysium Not the same as the muscle cell membrane Structural Organization of Skeletal Muscle Organ Tissue Cell Subcellular Cellular and Subcellular Skeletal Muscle Structure 1 Muscle cells are called fibers can be very large 100 mm in diameter many cm long 2 Typically multinucleate arising from fusion of myoblasts Muscle development Prior to birth increase in size After birth growth of muscle fibers happens by hypertrophy rather than hyperplasia muscle fibers cannot undergo mitosis Satellite cells have the ability to undergo mitosis after birth to aid in muscle regeneration increase in number 3 Functional Units of Organization 1 Conduction of electrical signals sarcolemma 2 Control of muscle contraction sarcoplasmic reticulum 3 Contraction myofibrils inside muscle fibers Conduction 1 Plasma membrane sarcolemma a surrounds cytoplasm b Transverse tubules T tubules arise from sarcolemma Control 2 Sarcoplasmic Reticulum smooth ER stores calcium a close proximity to T tubules b surrounds myofibrils sarcolemma calcium T tubule calcium SR SR calcium calcium Control Contraction 3 Myofibrils a longitudinal bundles of protein filaments inside the muscle fiber actin myosin b highly organized into repeating units SARCOMERES Clicker questions Clicker channel 70 Response Ware Session ID psio201 Which of the following is true about the connective tissue covering of muscle A Endomysium covers the muscle fascicle B Perimysium covers the myofibrils C Epimysium covers the muscle fiber D Deep fascia covers a group of muscles 63 24 8 A 5 B C D Which skeletal muscle structure stores calcium A Sarcolemma B Mitochondria C Sarcoplasmic reticulum D Myofibrils E Transverse tubules 97 2 A 0 B C 1 1 D E Which skeletal muscle structure contracts and generates force A Sarcolemma B Mitochondria C Sarcoplasmic reticulum D Myofibrils E Transverse tubules 92 4 A 0 2 B C 2 D E Sarcomeres sarcomere sarcomere sarcomere sarcomere Sarcomere I band thin filament incl actin A band I band thick filament myosin Sliding Filaments I band A band Shortening I band thin filament Sarcomere Muscle proteins 1 Contractile proteins Actin and myosin 2 Regulatory proteins Troponin and tropomyosin 3 Structural proteins Titin dystrophin actinin myomesin nebulin Contractile Proteins 1 Actin found in thin filaments has myosin binding sites for crossbridge formation with myosin 2 Myosin motor protein found in thick filaments has myosin head that binds to the myosin binding site on actin and forms crossbridge during muscle contraction Sarcomeres Functional Unit of Contraction Elements of Sarcomere Structure 1 Thin Filament Z Attached to Z line Z disc two twisted strands of pearls composed of two helically arranged strands of actin myosin binding site on actin covered by regulatory proteins troponin and tropomyosin Regulatory Proteins 1 Tropomyosin found in thin filaments covers the myosin binding sites on actin when muscle is relaxed 2 Troponin found in thin filaments holds tropomyosin in place when muscle is relaxed during contraction calcium binds to troponin and causes a conformational change that shifts tropomyosin away from the myosin binding sites on actin exposes the binding sites to allow crossbridge formation Sarcomeres Functional Unit of Contraction Elements of Sarcomere Structure 2 Thick Filament Z spans the distance and overlaps thin filaments imagine two golf clubs with their handles twisted about each other composed of a highly organized array of myosin molecules myosin head has ATPase activity when bound to actin Structural muscle proteins Titin spans half of each sarcomere from Z disc to M line stabilizes the position of the thick filament gives muscle its elasticity and extensibility and helps the sarcomere return to resting length after contraction Dystrophin Cytoskeletal protein that links the thin filaments to the sarcolemma Attached to the extracellular proteins in the connective tissues surrounding the muscle fibers Helps transmit tension from the sarcomeres to tendons Structural muscle proteins Nebulin spans the length of the thin filament anchors thin filaments to Z disc actinin found in the Z disc binds to actin molecules of the thin filament and to titin Myomesin Found in the M line Binds to titin and thick filaments to connect them together at the M line actinin myomesin Dystrophin Nebulin http droualb faculty mjc edu Lecture 20Notes Unit 203 chapter 9 skeletal muscle tiss 20with 20figures htm Sliding Filament Model of Muscle Contraction 1 Myosin heads bind to actin to form a crossbridge 2 Conformational change energized by ATP hydrolysis causes thin filaments to slide along thick filaments 3 Myosin head groups release form new crossbridges and the sliding cycle repeats Result Z lines move toward one another Sarcomere length decreases Myofibril shortens Muscle fiber shortens As Thick Thin filament overlap increases I band length decreases A band length remains constant H zone length decreases Zone of overlap increases Muscle contraction animation Cross Bridge Cycle animation captioned http www youtube com watch v Tuzr5N0TInM Suggested