KIN 3304 1nd Edition Lecture 6 Outline of Last Lecture I. Skeletal MuscleII. Neuromuscular Synapse (NMJ)III. Transverse (T) TubulesIV. Myofibrils and MyofilamentsV. Organization of SarcomereVI. Tropomyosin and TroponinVII. Thick FilamentVIII. TitinIX. Sliding Filament Theory (SFT)X. Electrical Events at Sarcolemma Surface Cause Muscle ActionXI. End of CycleOutline of Current Lecture I. Death in CirculationII. Motor UnitsIII. Skeletal Muscle Contracts when its MR are stimulatedIV. All of None PrincipleV. Rotating MU Recruitment Lessens Fatigue in MusclesVI. Muscle ToneVII. Muscle HypertrophyThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.VIII. How does Hypertrophy Occur?Current Lecture- KNOW STEPS IN MUSCLE CONTRACTION AND MUSCLE RELAXATIONI. Deatha. Death in Circulationi. Muscles deprived of nutrients, O2b. Muscle Fibers Depleted of ATPi. SR unable to remove Ca2+ii. Ca2+ ions diffuse in sarcoplasm1. Causes sustained muscle actionc. No ATP, cross-bridges cant detach from active sitesi. Muscle stays in “contracted” positiond. 15-25 hours later, enzymes break down MyofilamentsII. Motor Units (MU)a. All of the muscle fibers controlled by a single motor neuronb. Control from 1 to 1,000’s of fibersc. Stimulate MUi. Motor actiond. Figure 9.12: The Arrangement of MU in Skeletal MuscleIII. Skeletal Muscle Contracts when its MR are stimulateda. Dependent upon 2 factorsi. Frequency of stimulationii. Number of MU involvedb. A single, moment of contraction is called muscle twitchIV. All of None Principlea. Each fiber contracts completely or not at allb. All muscle fibers in a MU contract at same timei. Thus, exerted force depends on # of MU activatedii. Precise control of movement controlled by varying number of motor unitsV. Rotating MU Recruitment Lessens Fatigue in Musclesa. Muscle Fibers have a finite energy supplyb. During sustained exertion, MU are activated on rotating basisc. Some are at rest (recovery) and some are actively contractingVI. Energy Sources During Work (TQ)a. Type of Energy Available (graph)b. Four energy sourcesi. ATP1. Immediate (seconds or less)ii. ATP-PC1. Short term (<15 seconds)2. Sprinters extend this to go faster at endiii. Anaerobic Glycosis1. Minutes2. 800 mile runners/marathon runnersiv. Aerobic Glycosis1. Hoursv. We use all 4 of these at the same time but 1 is predominant.VII. Muscle Tonea. Some MU are always active (even at rest)b. Contractions don’t produce movement, but rather tensioni. This is called muscle tonec. Randomly selected MU keep constant tension in attached tendoni. Stabilizes bone/joint positionVIII. Muscle Hypertrophya. Results from repeated (exhaustive?) stimulusb. Fibers develop morei. Mitochondriaii. Glycolytic enzymesiii. Glycogen reservesc. Fibers contain more thick and thin filamentsi. Results in enlargement (hypertrophy) of stimulated musclesIX. How does Hypertrophy Occur?a. Occurs in muscles that have been repeatedly stimulated to produce near-maximal tensioni. Your athlete is now biggerb. Intracellular changes increases the amount of tension produced during muscle actioni. Your athlete is now
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