UMass Amherst KIN 470 - Kin 470 Final Exam Study Guide (35 pages)

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Kin 470 Final Exam Study Guide



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Kin 470 Final Exam Study Guide

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Pages:
35
School:
University of Massachusetts Amherst
Course:
Kin 470 - Exercise Physiology
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Kin 470 Final Exam Study Guide Muscle thermoregulation and physiology of training 1 What are the components of a motor unit a A motor unit is a motor neuron and all the fibers it innervates b Neuromuscular junction i Junction between motor neuron and muscle fiber c Motor end plate i Pocket formed around motor neuron by sarcolemma d Neuromuscular cleft i Short gap between neuron and muscle fiber e Acetylcholine is released from the motor neuron i Causes an end plate potential EPP ii Depolarization of muscle fiber 2 Describe the steps involved in excitation contraction coupling from activation of the alpha motor neuron to actomyosin binding a b Order of events i Release of Ach into NMJ ii Muscle cell action potential propogated iii Ca release from SR lateral sac iv Ca bind to Tn troponin removes blocking action of tropomyosin v Myosin binds to actin cross bridge moves vi Myosin power stroke generates force and or motion of actin filament vii Calcium taken up by SR viii Calcium removal from troponin restores tropomyosin blocking action 3 What are the molecular mechanisms underlying muscle relaxation a Cross bridge moves b Ca2 taken up by SR c Ca2 removal from troponin restores tropomyosin blocking action d relaxation e NOTES i Activation 1 Calcium released 2 Binds to troponin 3 Myosin binds to actin ii Relaxation 1 Calcium back to SR 2 Regulatory proteins prevent myosin and actin from binding 4 What is the role of troponin and tropomyosin in contraction a b troponin i blocks tropomyosin ii calcium binds to troponin allows myosin binding spots on actin to be exposed c tropomyosin i long stringy ii blocks the myosin binding sites on actin iii moves over to expose myosin binding spots on actin when calcium binds to troponin troponin blocking action removed 5 What are the molecular mechanisms that underlie muscle fatigue from intense contractile activity a b failure of Ca release from the sarcoplasmic reticulum c compromised activation of muscle less sensitive to Ca i no regulatory proteins ii TmTn regulate actomyosin interaction in a calcium dependent manner iii Pi and H depress sensitivity to Ca d accumulation of the metabolic byproducts of ATP hydrolysis i inorganic phosphate ii hydrogen ions iii stimulating fatigue in a single muscle fiber 1 H and Pi go back and forth between holes in sarcolemma 2 When pH decreased from 7 to 6 force declines by 50 3 Force declines to near 0 when 30 mM Pi is added to low pH solution 4 Force is restored when the fiber is placed back in the control solution iv Are Pi and H causative 1 Skinned single fiber preparations 2 Intracellular ion concentrations controlled so Pi and H can be increased to fatiguing levels in a rested fiber 3 Force measured under control condition pH 7 fiber maximally activated by Ca pCa 8 0 to 4 0 4 compared to maximal activation at pH 6 0 and force declines by 50 5 force declines further near 0 when 30mM Pi is added to low pH solution 6 force restored in control solution 7 proves that ions affect force producing capability of muscle 8 e two different types of fatigue i HF fatigue 1 Fatigue from high frequency stimulation of muscle 2 Fast running ii Low FF 1 Marathon running 2 Muscle stimulated at a much lower rate 3 Related to muscle glyogen depletion 6 Diagram the force length relationship of muscle and explain the underling basis if the shape of this relationship a b c d e there is an optimal length for force production if the length is too short or too long there is a lower force medium length is the best for force production NOTES i Length of sarcomeres ii Small scale stuff in muscle iii Around 2 2 5 micrometers iv Length where myosin and actin are most likely to interact v Most force possible vi Stretched really far can t reach low force vii Actin filaments cross each other myosin heads can t bind to correct filament no force 7 Plot the force velocity relationship of muscle and explain the implication of the shape a Force velocity relationship i Velocity of contraction depends on load ii As load increases velocity decreases iii The maximum velocity of shortening is greatest at the lowest force 1 True for both slow and fast twitch fibers b c d velocity vs force e as more force is produced the velocity of the muscle decreases f regulation of muscular force i size of muscle 1 fast motor units are generally larger ii number of motor units recruited 1 more recruited motor units more force iii rate at which motor units are recruited rate coding iv frequency of stimulation g muscle force power relationship h 8 What are the steps of the cross bridge cycle Be sure to show the mechanical and biochemical events a b ATP bound state rigor state c Release of Pi is closely associated with the force generation step d Increase Pi reversing this step by mass action pushing the CB back into this weakly bound or non force generating state e Elevating H affects the same step and thus reduces force f Protons affect ADP release step i Determines the shortening velocity and thus shortening velocity is reduced by increased H g Force and movement occurs when myosin releases these Pi and ADP h When Pi or H are high fatigue it reverses the force producing step i Muscles produce less force ii H may slow the release of ADP slow speed of shortening i What powers contraction And how is it coupled to movement force How is this coupled to ATP hydrolysis The cross bridge cycle i Ton is prolonged ii Could be a result of an extended time waiting for ADP release and or a prolongation of the time waiting for ATP to cause dissociation from actin iii Varying ATP concentration 1 Varying attachment time can estimate the separate durations of each kinetic step 2 Very High ATP this getts very small and the ton is mainly made up of ADP release rate j 9 What step in the cross bridge cycle limits contraction velocity a ADP release limits velocity b Protons affect ADP release step i Determines the shortening velocity and thus shortening velocity is reduced by increased H c When Pi or H are high fatigue it reverses the force producing step i Muscles produce less force ii H may slow the release of ADP slow speed of shortening 10 What key observations led to the sliding filament theory of contraction a Sliding filament model i Muscle shortening occurs due to the movement of the actin filament over the myosin filament ii Formation of cross bridges between actin and myosin filaments 1 Power stroke iii Reduction in the distance between Z lines of the sarcomere b Molecular


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