Kin 470 Final Exam Study GuideMuscle, thermoregulation, and physiology of training1. What are the components of a motor unit?a. A motor unit is a motor neuron and all the fibers it innervates.b. Neuromuscular junctioni. Junction between motor neuron and muscle fiberc. Motor end platei. Pocket formed around motor neuron by sarcolemmad. Neuromuscular clefti. Short gap between neuron and muscle fibere. Acetylcholine is released from the motor neuroni. Causes an end-plate potential (EPP)ii. Depolarization of muscle fiber2. Describe the steps involved in excitation-contraction coupling from activationof the alpha motor neuron to actomyosin binding.a.b. Order of events:i. Release of Ach into NMJii. Muscle cell action potential propogatediii. Ca++ release from SR lateral saciv. Ca++ bind to Tn (troponin) removes blocking action of tropomyosinv. Myosin binds to actin (cross bridge moves)vi. Myosin power stroke generates force and/or motion of actin filamentvii. Calcium taken up by SRviii. Calcium removal from troponin restores tropomyosin blocking action3. What are the molecular mechanisms underlying muscle relaxation?a. Cross-bridge movesb. Ca2+ taken up by SRc. Ca2+ removal from troponin restores tropomyosin blocking actiond.  relaxatione. NOTES:i. Activation1. Calcium released2. Binds to troponin3. Myosin binds to actinii. Relaxation1. Calcium back to SR2. Regulatory proteins prevent myosin and actin from binding4. What is the role of troponin and tropomyosin in contraction?a.b. troponini. blocks tropomyosinii. calcium binds to troponin, allows myosin binding spots on actin to be exposed c. tropomyosini. long & stringyii. blocks the myosin binding sites on actiniii. moves over to expose myosin binding spots on actin when calcium binds to troponin, troponin blocking action removed5. What are the molecular mechanisms that underlie muscle fatigue from intense contractile activity?a.b. failure of Ca++ release from the sarcoplasmic reticulumc. compromised activation of muscle (less sensitive to Ca++)i. no regulatory proteinsii. TmTn regulate actomyosin interaction in a calcium dependent manneriii. Pi and H+ depress sensitivity to Ca++d. accumulation of the metabolic byproducts of ATP-hydrolysisi. inorganic phosphateii. hydrogen ionsiii. stimulating fatigue in a single muscle fiber;1. H+ and Pi go back and forth between holes in sarcolemma2. 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 solution4. Force is restored when the fiber is placed back in the control solutioniv. Are Pi and H+ causative?1. Skinned single fiber preparations2. Intracellular ion concentrations controlled so Pi and H+ can be increased to fatiguing levels in a rested fiber3. 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 solution6. force restored in control solution7. proves that ions affect force producing capability of muscle8.e. two different types of fatigue:i. HF fatigue1. Fatigue from high frequency stimulation of muscle2. Fast runningii. Low FF1. Marathon running2. Muscle stimulated at a much lower rate3. Related to muscle glyogen depletion6. Diagram the force-length relationship of muscle and explain the underling basis if the shape of this relationship.a.b. there is an optimal length for force productionc. if the length is too short or too long there is a lower forced. medium length is the best for force productione. NOTES:i. Length of sarcomeresii. Small scale stuff in muscleiii. Around 2-2.5 micrometersiv. Length where myosin and actin are most likely to interactv. Most force possiblevi. Stretched really far: can’t reach, low forcevii. Actin filaments cross each other, myosin heads can’t bind to correct filament no force7. Plot the force-velocity relationship of muscle and explain the implication of the shape.a. Force-velocity relationshipi. Velocity of contraction depends on loadii. As load increases, velocity decreasesiii. The maximum velocity of shortening is greatest at the lowest force1. True for both slow- and fast-twitch fibersb.c.d. velocity vs. forcee. as more force is produced, the velocity of the muscle decreasesf. regulation of muscular force:i. size of muscle1. fast motor units are generally largerii. number of motor units recruited1. more recruited motor units = more forceiii. rate at which motor units are recruited (rate coding)iv. frequency of stimulationg. muscle force-power relationshiph.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 statec. Release of Pi is closely associated with the force generation stepd. Increase Pi  reversing this step by mass action pushing the CB back into this weakly bound or non-force generating statee. Elevating H+  affects the same step and thus reduces forcef. Protons affect ADP release stepi. Determines the shortening velocity and thus shortening velocity is reduced by increased H+g. Force and movement occurs when myosin releases these Pi and ADPh. When Pi or H+ are high (fatigue) it reverses the force producing stepi. Muscles produce less forceii. H+ may slow the release of ADP, slow speed of shorteningi. What powers contraction? And how is it coupled to movement/force? How is this coupled to ATP hydrolysis: The cross bridge cyclei. 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 actiniii. Varying ATP concentration;1. Varying attachment time can estimate the separate durations of each kinetic step2. Very High ATP this getts very small and the ton is mainly made up of ADP release ratej.9. What step in the cross-bridge cycle limits contraction velocity?a. ADP release limits velocityb. Protons affect ADP release stepi. 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 stepi. Muscles produce less forceii. H+ may slow the release of ADP, slow speed of shortening10. What key observations led to the sliding filament theory of contraction?a. Sliding filament modeli. Muscle shortening occurs due to the movement of the actin filament over the myosin filamentii. Formation of cross bridges between actin