Unit 3 Lecture 5 Notes Mitochondria I Muscle Metabolism Energy for contraction process coms from ATP produced in a ATP provides energy for coupling of myosin cross bridges with actin pulling the actin operating the calcium pump removes calcium back into the terminal cisternae b While active site is being exposed cross bridge is being cocked or put into a position of high energy i ATP hydrolysis occurs and causes ATP to break down into ADP Phosphate group Pi This provides energy for power stroke sequence ii Myosin bridge head attaches to active site high energy iii Power stroke begins 1 Myosin head pivots 2 Pulls actin filament 3 High energy to low energy bent configuration 4 Uses up the energy 5 ADP and Pi are released from the myosin head 6 New ATP attached to uncocked myosin head and allows myosin head to release from the actin binding site 7 cocking process begins again c Sources of ATP i ATP stored in myosin head is immediately available in a small amount used up in 6 seconds ANAEROBIC w o oxygen ii Metabolic pathways proved ATP 2 anaerobic and 1 aerobic w oxygen iii ADP CP system ANAEROBIC 1 CP creatine Phosphate high energy compound stored in 2 After myosin head ATP is gone CP ADP ATP Creatine 3 5 times more CP stores in muscle than ATP depleted in 10 15 iv Glycolysis ANAEROBIC 1 1st step in breakdown of glucose major fuel source of cellular muscle seconds energy 2 occurs in cytoplasm and produces pyruvic acid and 2 ATP 3 40 seconds 4 Glucose pyruvic acid 2 ATP a few minutes v Oxidative Phosphorylation AEROBIC 1 Most ATP formed by this process 2 Glucose completely broken down forms carbon dioxide water and many ATP 3 Glucose O2 CO2 H2O 36 ATP 4 Occurs in mitochondria 5 Prolonged 5 minutes and submaximal activity vi Summary 1 Pyruvic acid glycolysis converted to lactic acid 2 Lactic acid becomes product of glycolysis instead of CO2 and H2O lactic acid accumulates II Muscle Fatigue muscle has physiological inability to contract a Use ATP faster than it is produced ATP deficit b State of continuous or spasmodic contraction Muscle cramp i Cross bridges cant release calcium to relax c Contributing factors III Oxygen consumption i Lactic Acid accumulates changed muscle pH and fibers less ii responsive to stimulation Ionic imbalances inability of sodium potassium pump to function no ATP a After exercise body still needs oxygen breathing heavy until body recovers i Amount of oxygen consumed during recovery period Recovery 1 Old term oxygen debt amount needed to restore resting Oxygen Consumption metabolic state ii Recovery oxygen consumption 1 Restore muscles to resting metabolic condition convert lactic acid to pyruvic acid and replenishes glycogen CP and ATP 2 Satisfy post exercise metabolism exercise elevates body 3 temperature increases rate of chemical reactions Increases heart rate and muscles of respiration requires more oxygen and ATP 4 Repair damaged tissue total O2 depends on exercise duration intensity and physical condition IV Muscle contraction a Factors effecting the amount of tension muscle generates i Number and size of fibers 1 More fibers greater tension 2 Larger fibers more myofibrils greater tension a Both measured by cross sectional area of muscle belly b Greater cross section more or larger fibers stronger ii Series elastic elements SEE muscle 1 Muscle pulls on CT endo peri epimysium CT is elastic 2 Stretched and released elastic recoil Add to muscle force a Counter movement aspects of jumping b Flex and hold see NO benefit c Stored energy dissipates iii Initial length of fibers 1 Muscle slightly stretched More Force 2 Actin and myosin just overlap in stretched position a Can slide over greater distance and produce more tension 3 Resting length near optimal 4 Forced greatly reduced when muscles stretched far actin pulled beyond myosin cross bridges and muscle shortened too much actin and myosin completely overlap iv Metabolic condition need O2 nutrients and clear wastes v Number of fibers recruited not all contracted at once only for maximal contraction 1 Sub maximal contraction amount of force tension depends on the number of fibers actually contracting functioning 2 Number of fibers acting is influenced by a Adequate stimulus i Threshold minimum stimulus for contraction 1 Strength and duration 2 Fiber will contract completely 3 All or None principle fiber function All myofibrils in ii Sub threshold no contraction b Number of fibers in motor unit MU single nerve and muscle fibers it innervates i Threshold stimulates from nerve to muscle 1 All fibers in motor unit contract 2 More fibers in motor unit greater 3 Larger muscles average 150 per motor 4 Fine control muscles eye finger 4 per tension unit motor unit ii Fibers in MU not grouped together scattered through muscle iii Contraction occurs over broad area iv RECRUITMENT Strong stimulus more MU greater force increased load also increases amount of force vi Fiber arrangement 1 Parallel arrangement relatively weak 2 Pennate and convergent arrangements are stronger b Speed of Muscle contraction i Not all muscles contract the same 1 Eye muscle 10 times faster than posture muscles slowest 2 Limb muscles medium speed ii Muscle Fiber types a Pathway for ATP synthesis i Aerobic ii Anaerobic pathways oxidative fibers pathways glycolytic fibers b Amount of myoglobin i Lots red fibers ii Little White fibers c ATPase enzyme decompose ATP i Fast acting fast twitch ii Slow acting slow twitch 2 STFR fibers Slow Twitch Fatigue Resistant red or slow oxidative a Small red cells slow acting ATPase b Lots of myoglobin red color c Lots of mitochondria and aerobic pathways O2 d Fatigue resistant endurance muscles and strong prolonged Fast twitch Fatigable 3 FTF white or fast glycolytic fibers a White cells 2x diameter of STFR powerful b Little myoglobin Anaerobic no O2 c Fast acting ATPases contract rapidly and use lots of d Fatigue easily rapid intense movements 4 FTFR Fast Twitch Fatigue Resistant Pale or Fast Oxidative glycogen fibers a PINK cells Intermediate in size b Fast ATPases Mostly aerobic pathways c Oxygen dependence and myoglobin like slow twitch d Fatigue resistant not as much as slow twitch 5 Most muscles have mixed fiber types but a single Motor Unit MU genetically controlled a Posture used MU with slow twitch fibers b Arms and hands more FTF fibers c Low back more STFR fibers d Marathon runners more STFR e Sprinters more fast twitch f Weight lifters equal amounts fast and slow iii Size of Load 1 Heavier load