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PHYSIOLOGY OF EXERCISE PET 3380 REVIEW GUIDE FOR EXAM 3 Structural Aspects of Skeletal Muscle 1 Know what general proteins that comprise the thick and thin filaments a Thick Filaments actin cycling filament fiber surface function i Myosin Splits ATP and is responsible for the power stroke of the myosin head ii C protein holds myosin thick filaments in a regular array controls of myosin molecules in a thick filament iii M protein helps hold thick filaments in a regular array iv Myomesin provides a strong anchoring point for the protein titin v M CK provides ATP from phosphocreatine located proximal to the myosin heads b Thin Filaments i Actin interacts with myosin during excitation contraction coupling ii Tropomyosin transduces the conformational change of the troponin complex to iii Troponin Binds Ca2 and affects tropomyosin signal that induces crossbridge iv Nebulikn control the number of actin monomers joined to each other in thin 2 Know what the sarcolemma and sarcoplasm are a Sarcolemma thin elastic membrane that encloses the fiber s cellular contents i Plasma membrane conducts electrochemical wave of depolarization over muscle 1 Caveolae allows for lengthening of plasma membrane 2 More selective to ions solutes and substrates crossing it and critical for cell ii Basement membrane fuses with tendon bone iii Satellite Cells between Plasma and Basement membrane myogenic stem cells b Sarcoplasm cytoplasm contains proteins minerals fats organelles glycogen and myoglobin 3 Know what the t tubules and sarcoplasmic reticulum are a Transverse Tubules T tubules Transport system deep into fiber allows rapid conduction of b Sarcoplasmic Reticulum SR membranous channel parallel to myofibril and storage site for impulse calcium 4 What is a sarcomere and what are its boundaries a Sarcomere smallest contractile unit of skeletal muscle fiber i Boundaries Z disc to Z disc 5 Functional importance of muscle fiber to muscle length ratio a Muscle Fiber to Muscle Length Ratio varies between 0 2 and 0 6 b Short Muscle Fiber and Short Muscle Length produces more force and velocity low ratio c Long Muscle Fiber and Long Muscle Length produces less force and velocity high ratio i Quadriceps and plantar flexors i Hamstrings and dorsiflexor 6 How do endurance and resistance training affect the size of a muscle fiber and why is this case in terms of diffusion of O2 and other nutrients to the center of the muscle a 7 Know the differences between muscle fiber types I IIA IIX in terms of myosin ATPase activity shortening velocity mitochondrial and capillary density cross sectional area and in general what sports and activities fast IIA IIX and slow I fibers support Also know general rates of fatigue of each fiber a Fast Twitch Fibers i High capability for electrochemical transmission of action potentials ii High myosin ATPase activity iii Rapid CA2 release and uptake by an efficient sarcoplasmic reticulum iv High rate of crossbridge turnover v Sports Stop and Go basketball soccer lacrosse or field hockey vi Large cross sectional area vii Quick to fatigue viii Muscle Type 1 2 IIA fast shortening speed and moderately well developed capacity for energy transfer from both aerobic and anaerobic sources IIX paid shortening velocity true fast twitch fibers b Slow Twitch Fibers i Low myosin ATPase activity ii Slow calcium handling ability and shortening speed iii Less well developed glycolytic capacity than fast twitch fibers iv Large and numerous mitochondria higher capillary density v Sports endurance sports vi Smaller cross sectional area vii Fatigue resistant viii Muscle Type 8 Know any exercise induced adaptations 1 I slow twitch fibers a Type of exercises helps shift fiber type slightly to type of training i Explosive power training builds more fast twitch fibers ii Aerobic Training builds more slow twitch fibers Muscular Contraction 1 What mineral is the key to muscular contraction a Calcium Ca2 binds to troponin complex to open up the Actin active site 2 Know the role of troponin and tropomyosin in muscular contraction a Troponin a complex of three regulatory proteins troponin C troponin I and troponin T that is integral to muscle contraction i Contains binding site for calcium to open up the Actin active site b Tropomyosin protein attached to troponin that blocks the actin active site 3 Describe the chemical and mechanical steps in the cross bridge cycle and explain how the cross bridge cycle results in shortening of the muscle Sliding Filament Hypothesis and Hypothetical scheme of cross bridge cycle etc a Sliding Filament Theory muscle shortens or lengthens because the thick and thin filaments slide past each other without changing length The myosin crossbridges attach rotate and detach from the actin filaments with energy from ATP hydrolysis to drive fiber shortening i Controversy multiple cross bridge cycles occur foe each ATP hydrolyzed b Hypothetical scheme of cross bridge cycle i Step 1 Ca2 is released from the SR and the myosin head attaches to actin ii Step 2 Tension is developed and movement occurs with the release of ADP and Pi iii Step 3 Actin and myosin dissociates in the presence of ATP iv Step 4 ATP is hydrolyzed and Myosin is energized and return to resting state c working stroke cross bridge moves an actin filament through 10nm in the space of 2ms while hydrolyzing 1 ATP molecule 4 Principles theories and relationships e g size principle length tension relationship and etc a Length tension Optimum Length 2 05 2 2uM i Greatest overlap that allows for the highest active tension ii Too long there is no myosin actin overlap or tension iii Too Short sarcomere interfere with each other b Force Velocity inversely related i More Force less velocity ii More Velocity less force 5 Know Excitation Contraction EC coupling Be able to describe the sequences involved in EC Coupling muscle contraction from release of ACH from the motor neuron all the way until relaxation a Excitation Contraction physiological process of converting an electrical stimulus to mechanical response i Sequence 1 An action potential from CNS reaches a motor neuron which then transmits the action potential down its own axon 2 Action potential activates voltage dependent Ca2 channels on the axon and 3 Ca2 rushes in Increase in Ca2 causes synaptic vesicles containing Ach to fuse with the plasma membrane at active zone 4 ACh is released in the synaptic cleft where it binds and activates nicotinic Ach receptor on motor end plate 5 Na


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FSU PET 3380C - Structural Aspects of Skeletal Muscle

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