KIN 3304 1nd Edition Lecture 6 Outline of Last Lecture I Skeletal Muscle II Neuromuscular Synapse NMJ III Transverse T Tubules IV Myofibrils and Myofilaments V Organization of Sarcomere VI Tropomyosin and Troponin VII Thick Filament VIII Titin IX Sliding Filament Theory SFT X Electrical Events at Sarcolemma Surface Cause Muscle Action XI End of Cycle Outline of Current Lecture I Death in Circulation II III Motor Units Skeletal Muscle Contracts when its MR are stimulated IV V All of None Principle Rotating MU Recruitment Lessens Fatigue in Muscles VI Muscle Tone VII Muscle Hypertrophy These 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 I KNOW STEPS IN MUSCLE CONTRACTION AND MUSCLE RELAXATION Death a Death in Circulation i Muscles deprived of nutrients O2 b Muscle Fibers Depleted of ATP i SR unable to remove Ca2 ii Ca2 ions diffuse in sarcoplasm 1 Causes sustained muscle action c No ATP cross bridges cant detach from active sites i Muscle stays in contracted position d 15 25 hours later enzymes break down Myofilaments II Motor Units MU a All of the muscle fibers controlled by a single motor neuron b Control from 1 to 1 000 s of fibers c Stimulate MU i Motor action d Figure 9 12 The Arrangement of MU in Skeletal Muscle III Skeletal Muscle Contracts when its MR are stimulated a Dependent upon 2 factors i Frequency of stimulation ii Number of MU involved b A single moment of contraction is called muscle twitch IV All of None Principle a Each fiber contracts completely or not at all b All muscle fibers in a MU contract at same time i Thus exerted force depends on of MU activated ii Precise control of movement controlled by varying number of motor units Rotating MU Recruitment Lessens Fatigue in Muscles a Muscle Fibers have a finite energy supply b During sustained exertion MU are activated on rotating basis c Some are at rest recovery and some are actively contracting V VI Energy Sources During Work TQ a Type of Energy Available graph b Four energy sources i ATP ii iii iv v 1 Immediate seconds or less ATP PC 1 Short term 15 seconds 2 Sprinters extend this to go faster at end Anaerobic Glycosis 1 Minutes 2 800 mile runners marathon runners Aerobic Glycosis 1 Hours We use all 4 of these at the same time but 1 is predominant VII Muscle Tone a Some MU are always active even at rest b Contractions don t produce movement but rather tension i This is called muscle tone c Randomly selected MU keep constant tension in attached tendon i Stabilizes bone joint position VIII Muscle Hypertrophy a Results from repeated exhaustive stimulus b Fibers develop more i Mitochondria ii Glycolytic enzymes iii Glycogen reserves c Fibers contain more thick and thin filaments i Results in enlargement hypertrophy of stimulated muscles IX How does Hypertrophy Occur a Occurs in muscles that have been repeatedly stimulated to produce nearmaximal tension i Your athlete is now bigger b Intracellular changes increases the amount of tension produced during muscle action i Your athlete is now stronger
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