KINS 1223 Unit 3 Lecture 4 Study Guide Muscle Metabolism Energy for contraction process comes from ATP produced in mitochondria ATP provides energy for 1 Coupling of myosin cross bridges with actin 2 Pulling the actin 3 Operating the Ca pump removes Ca back into terminal cisternae While active site is being exposed Cross bridge is being cocked put into high energy position ATP hydrolysis occurs causes ATP to break down into ADP Pi high energy phosphate which provides energy for power stroke sequence Myosin cross bridge head attach to active site in high energy position Power stroke begins Myosin head pivots Pulls actin filament High energy to low energy bent configuration Use up the energy ADP and Pi are released from the myosin head New ATP attaches to uncocked myosin head allowing the myosin head to release from actin binding site Cocking process begins again Sources of ATP 1 ATP stored on myosin head a Small amount immediately available and used up in 6 seconds b Anaerobic 2 ADP CP creatine phosphate system a Creatine Phosphate high energy compound stored in muscle 5X more CP than ATP in muscle and depleted in 10 15 seconds b After myosin head ATP is gone CP ADP ATP Creatine c Anaerobic d ATP ADP CP 15 20 sec of energy 100m dash without breathing 3 Glycolysis a 1st step in breakdown of glucose major fuel source for cellular energy b Occurs in cytoplasm and produces pyruvic acid and 2 ATP Glucose Pyruvic acid 2 ATP 4 Oxidative Phosphorylation a Most ATP formed by this process b Aerobic c Glucose broken down in mitochondria Glucose O2 CO2 H2O 36 ATP over 5min submaximal activity d Prolonged Summary Myosin Head Anaerobic 6 seconds ADP CP Anaerobic 10 15 seconds Glycolysis Anaerobic 40sec to a few minutes Oxidative Phosphorylation Aerobic Submaximal over 5min Vigorous brief exercise ATP supplied anaerobically Prolonged contractions body can t keep pace with demand for O2 to run systems that supply ATP Inadequate oxygen Pyruvic acid glycolysis converted to lactic acid Lactic acid becomes product of glycolysis and accumulates Muscle Fatigue Physiological inability to contract Use ATP faster than it is produced ATP deficit not absence State of continuous or spasmodic contraction muscle cramp Cross bridges can t release to relax Contributing factors Lactic acid accumulates changes muscle pH making fibers less responsive to stimulation Ionic imbalances inability of Na K pump to function because there is no ATP After exercise body still needs O2 so it breathes heavily until it recovers Recovery Oxygen Consumption is amount needed to restore resting metabolic state old Oxygen consumption term oxygen debt Includes O2 needed to 1 Restore muscles to resting metabolic condition a Convert lactic acid to pyruvic acid b Replenish Glycogen CP and ATP 2 Satisfy post exercise metabolism reactions so more O2 needed for ATP 3 Increases HR muscles of respiration a Requires more O2 and ATP 4 Repair damaged tissue a Exercise elevates body temperature increases rate of chemical a Total O2 depends on exercise duration intensity physical condition Factors affecting the amount of tension a muscle generates 1 Number and size of fibers a More fibers more tension b Larger fibers more myofibrils larger tension c Both measured by cross sectional area of belly greater x sect more fibers stronger muscle 2 Series elastic elements SEE a Muscle pulls on CT endo peri Epimysium b Elastic CT is stretched released elastic recoil Adds to muscle force counter movement aspects of jumping 3 Initial length of fibers a Muscle slightly stretched More force b Actin Myosin just overlap in stretched position Can slide over greater distance produce more tension c Resting length near optimal 2 2 5 m 4 Metabolic condition a Needs O2 nutrients to clear wastes 5 Number of fibers recruited Not all contracted at once Maximal contraction need all Sub maximal contraction b Number of fibers acting influenced by Adequate Stimulus a Amount of force tension depends on number of fibers actually contracting o Threshold minimum stimulus for contraction o All or none principle Fibers will contract completely All myofibrils in fiber function o Sub threshold no contraction o Muscle fibers have different thresholds Number of fibers in motor unit single nerve muscle fibers it innervates o Threshold stimulus from nerve to muscle All fibers in motor unit contract more fibers greater tension Large muscles average 150 motor unit fine control muscles 4 motor unit o Fibers in motor units not grouped together but scattered throughout the muscle contraction occurs over broad area o Strong stimulus more motor units greater force Recruitment o Increased load stimulus increases amount of force 6 Fiber arrangement a Parallel arrangement relatively weak b Pennate and convergent arrangements are stronger Speed of Muscle Contraction Not all muscles contract at same speed Eye muscles 10X faster than posture muscles slowest Limb muscles medium speed Factors influencing speed of contraction 1 Muscle fiber type a All muscles NOT physiologically alike based on Pathway for ATP synthesis 1 Aerobic pathways 2 Anaerobic pathways Oxidative fibers Glycolytic fibers Amount of myoglobin 1 Lots Red fibers 2 Little White fibers ATPase enzyme decompose ATP 1 Fast acting Fast twitch a Fast Twitch Fatigable FTF Pale white or Fast Glycolytic fibers i 2X diameter of STFR ii Powerful but fatigue easily iii Little myoglobin lots of Glycogen iv Anaerobic v Fact acting ATPases contract rapidly causing rapid intense movements b Fast Twitch Fatigue Resistant FTFR Pale or Fast Oxidative fibers i Pink cells intermediate in size ii Fast ATPases iii O2 dependence myoglobin like slow twitch iv Mostly aerobic pathways v Fatigue resistant not as much as slow twitch 2 Slow acting Slow twitch a Slow Twitch Fatigue Resistant STFR Red or slow oxidative fibers i Small RED cells color given by lots of myoglobin ii Slow acting ATPases iii Lots of mitochondria iv Aerobic pathways v Fatigue resistant strong endurance muscles b Most muscles have mixed fiber types c Single motor unit all the same d Fast movement select motor units with fast twitch fibers e Specialized muscles Arms hands more FTF fibers Low Back posture STFR fibers f Athletes have more of one fiber type Marathon runners more STFR Sprinters more Fast Twitch Weight lifters equal amounts fast and slow g Genetically controlled not training controlled 2 Size of load a Heavier load greater stimulus Increase force of contraction up to a point b