EXAM 3 REVIEW SHEET MUSCULAR SYSTEM 1 Endomysium delicate CT membrane that surrounds each muscle fiber 2 Perimysium coarse CT membrane that surrounds each fascicle 3 Epimysium tough CT membrane that surrounds group of fascicles 4 Fascicle bundle of endomysium covered muscle fibers wrapped in perimysium 5 Tendon cord of dense fibrous tissue attaching muscle to bone 6 Sarcolemma plasma membrane of muscle fiber 7 Sarcoplasm cytoplasm of muscle iber 8 Sarcoplasmic reticulum SR specialized smooth ER stores releases calcium into sarcoplsam 9 Myoglobin red pigment that bings and stores oxygen 10 Sarcomere structural unit of skeletal muscle smallest contractile unit in skeletal muscle a Distance between 2 successive Z lines b Contains A band M line thin filaments Z lines H zone I bands 11 A band thick filament 12 Z line anchors thin filaments 13 H zone middle region of A band not overlapping with thin filaments 14 I band regions of thin filaments not overlapping with A band 15 Triad transverse tubule between 2 terminal cisternae a Releases calcium ions into sarcoplasm when sarcolemma depolarizes 16 Motor unit motor neuron and all the skeletal muscle fibers it innervates via axonal termnals 17 NEUROMUSCULAR JUNCTION junction between axonal terminal of motor neuron and skeletal muscle fiber separated by neuromuscular cleft a Only 1 neuromuscular junction per muscle fiber b Motor end plate highly folded region of sarcolemma of muscle fiber at neuromuscular junction i Has highest number of acetylcholine receptors 18 PROTEINS IN THIN FILAMENT a Actin contains binding sites for myosin heads b Tropomyosin rod shaped regulatory protein that spirals around actin and blocks myosin binding sites on actin in relaxed skeletal muscle c Troponin 3 polypeptide complex i TnC binds calcium ions ii TnT binds to tropomyosin iii TnI inhibitory subunit that binds to actin 19 ACTIVATION OF MYOSIN HEADS a ATPase splits ATP into ADP Pi inorganic phosphate still attached to myosin globular heads activated 20 SKELETAL MUSLCE CONTRACTION E C Coupling a Motor neuron activated b Axon of motor neuron generates transmits action potential to axon terminals triads sarcoplasm on actin c ACh released from vesicles in axon terminals into neuromuscular cleft d ACh binds to receptors on motor end plate depolarization generation of action potential at motor end plate e Action potential spreads across sarcolemma and into T tubules of f Calcium ions released from terminal cisternae of triads into g Calcium ions bind to TnC conformational change removal of tropomyosin from blocking myosin binding sites on actin h Myosin heads activated attached by ADP Pi i Activated myosin heads cross bridges bind to myosin binding sites j ADP Pi dissociate from cross bridges POWERSTROKE i Attached cross bridges change orientation from right angle to bent position sliding of thin filaments skeletal muscle contraction 21 ROLE OF ATP IN MUSCLE CONTRACTION a ATP hydrolyzed by ATPase to produce ADP and Pi activates myosin heads b ATP required for crossbridge detachment c ATP required for sequestration confiscation of calcium ions back into SR for storage active transport 22 Rigor mortis lack of new ATP skeletal muscle contracture a Occurs when person dies ATP synthesis stops actin and myosin are cross linked and skeletal muscles remain contracted 23 Muscle fatigue physiological inability of stimulated skeletal muscle to contract b c of ATP deficit a ATP production ATP demand 24 SLIDING FILAMENT MECHANISM sliding of thin filaments past A bands results in muscle contraction a Structures that shorten when skeletal muscles contract i H zone ii I bands iii Sarcomere length iv Skeletal muscle i A bands ii Thin filaments b Structures that remain the same when skeletal muscles contract 25 FACTORS THAT AFFECT STRENGTH OF SKELETAL CONTRACTION a Size of motor units activated i Larger motor units more force b Number of motor units activated i Force increases as of motor units activated increases ii Smaller motor units activated first c Frequency of skeletal muscle activation i Force increases as rate of stimulation by motor neurons increases d Length of sarcomeres prior to contraction i Sarcomeres at optimum length maximum force 1 Optimum length slight overlap b w A bands and thin filaments with H zone ii Shortened sarcomeres decreased force 1 Shortened complete overlap b w A bands and thin filaments but there is NO H zone 2 Zero force generated b c no H zone to slide into iii Stretched sarcomeres decreased force 1 Stretched no overlap b w A bands and thin ilaments 26 3 TYPES OF SKELETAL MUSCLE FIBERS a Slow Oxidative Fibers slow hydrolyzation of ATP aerobic respiration i Highest content of myoglobin binds releases oxygen ii AKA RED FIBERS b c high content of red myoglobin iii Predominant in muscles involved in endurance activities postural muscles iv Suited for far endurance events running marathon b Fast Oxidative Fibers fast hydrolyzaton of ATP aerobic respiration c Fast Glycolytic Fibers fast hydrolyzation of ATP anaerobic respiration using more glycogen i Lowest myoglobin appear white WHITE FIBERS ii Used in activities that are short lived but intense iii More in chest and back muscles 27 Isotonic contractions muscle shortens at relatively constant force a Force generated by skeletal muscle exceeds weight 28 Isometric contractions force generated by muscle is increasing at constant b Ex Lifting weights muscle length a Weight exceeds force generated by muscle b Ex Holding box in front of you 29 SKELETAL VS SMOOTH MUSCLE CONTRACTION a Smooth muscle requires entry of extracellular calcium into sarcoplasm b Skeletal muscle does not require entry of extracellular Ca2 30 STRUCTURES PRESENT IN SKELETAL MUSCLE FIBERST THAT ARE ABSENT FROM SMOOTH MUSCLE CELLS a Smooth muscle cells lack striations thin and thick filaments arranged diagonally b Smooth muscle lacks sarcomeres CALMODULIN d Smooth muscle cells lacks Z lines c Thin filaments in smooth muscle lack troponin calcium binds to e Smooth muscle cells contain DENSE BODIES to anchor thin filaments f Smooth muscle cells contain INTERMEDIATE FILAMENTS that resist tension i Not in skeletal muscle fibers g Sarcolemma of smooth muscle cells lacks T tubules sarcolemma has CAVEOLI that have extracellular fluid rich in calcium 31 SINGLE UNIT SMOOTH MUSCLES a Circular and longitudinal smooth muscle sheets b Innervated by autonomic nerve fibers c Electrically coupled by gap junctions contracts as unit d Stimulated to
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