Ch 9 Muscles and Muscle Tissue … V. ATP for Muscle Contraction

V. ATP for Muscle Contraction (Muscle Metabolism) A. Providing Energy For Contraction 1. ATP is The Only Direct Source of Energy Limited amount stored in muscles = 4-6 seconds Chemical Reacton: ATP ↔ ADP + Pi + Energy Regenerated immediately by chemical pathways: Creatine Phosphate, Anaerobic & Aerobic Respiration Prolonged-duration exercise Short-duration exercise Stored ATP. Anaerobic Pathway). Aerobic Pathway. creatine phosphate 6 seconds 10 seconds 30–40 seconds End of exercise Hours Figure 9.20 Comparison of energy sources used during short-duration exercise and prolonged-duration exercise.

2. Aerobic Respiration– For Rest & Normal Activity a) Produced where? By what Organelle? b) Reactants needed? c) Products produced? d) Is a complex set of chemical reactions i) Glycolysis Breaks Glucose up into two 3-carbon molecules of Pyruvic Acid Occurs in the cell’s cytoplasm Creates just a few ATP by itself Pyruvic Acid enters mitochondria and is completely broken down to create many more ATP ii) Mitochondria Citric Acid Cycle Electron Transport Chain most ATP made with this pathway

e) Carbon Dioxide goes where? f) Fuel converted to ATP Blood Glucose 2. Aerobic Respiration … e) Carbon Dioxide goes where? f) Fuel converted to ATP Blood Glucose Stored Glycogen Fatty Acids– after 30 minutes, stored fat is main energy source Source of O2: breathing & myoglobin g) Efficency: 1 glucose  36 ATP h) Speed of reactions: Slow i) How long one can do it: hours j) Type of Exercise Can Be Used For: moderate k) Size of Muscle: All, especially small

3. ATP During Vigorous Exercise As Exercise level increases to vigorous, the ATP generated by Aerobic Respiration becomes inadequate a) Use of Creatine Phosphate to make more ATP i) Creatine Phosphate = high energy chemical ii) Stored in muscles iii) CP Transfers Phosphate to ADP forming ATP iv) No Oxyegen required v) Next 10-15 seconds b) Anaerobic Respiration i) Oxygen needed? ii) Fuel = blood glucose OR stored glycogen iii) Uses Anaerobic Glycolysis Location: Cell’s cytoplasm

1 Glucose  2 Pyruvic Acids, to make 2 ATP very fast iii) Uses Anaerobic Glycolysis … 1 Glucose  2 Pyruvic Acids, to make 2 ATP very fast  Lactic Acid is made from the Pyruvic Acids = waste product, slight toxic Pain the Next Day: Caused by It’s Accumulation; Must be converted to less toxic iv) Efficiency: Incomplete breakdown of Glucose; 5% ATP v) Speed: Fast vi) Time Span: 30-40 seconds vii) Muscle Type: especially large viii) Type of Exercise: Only during vigorous exercise Figure 6.10c

Review of ATP Generation And Use Figure 9.20 Comparison of energy sources used during short-duration exercise and prolonged-duration exercise. Review of ATP Generation And Use Short-duration exercise Prolonged-duration exercise 6 seconds 10 seconds 30–40 seconds End of exercise Hours ATP stored in muscles is used first. ATP is formed from creatine phosphate and ADP (direct phosphorylation). Glycogen stored in muscles is broken down to glucose, which is oxidized to generate ATP (anaerobic pathway). ATP is generated by breakdown of several nutrient energy fuels by aerobic pathway. © 2013 Pearson Education, Inc.

A. Providing Energy For Contraction … 4. Energy Systems Used during Exercise Aerobic R.– used soley as long as the slow rate of ATP production is adequate Marathons– ATP generated =rate produced Aerobic Endurance: time can continue Aerobic R Exercise for Short Surge of Power: Stored ATP/CP; Weight Lifting, Diving, Sprinting Exercise for Longer Surge of Power: Anaerobic R. Tennis, Soccer, 100 m run/swim Power no longer needed  Aerobic R But Time Limit: 1- 1 ½ minutes max.

B. Muscle Fatigue = physiological inability of muscle to contract even with stimulus Causes Not completely understood Ionic Imbalances: Accumulation of inorganic Phosphate interferes with Ca release from SR which alters excitation-contraction coupling Primarily w/ short duration of intense exercise Recovery is usually rapid

C. Excess Postexercise Oxygen Consumption (EPOC) 1. EPOC (oxygen debt) = Extra O2 needed immediately after Anaerobic Respiration to restore resting state: Restore ATP, CP, O2 reserves in myoglobin Convert Lactic acid  Pyruvic Acid Restore glycogen stores How long this takes determines recovery time = when are ready to do Anaerobic R. again (Health Measure) 2. Aerobic Respiration is Required: So extra vigorous breathing after Anaerobic R. brings in the needed O2 for Aerobic Respiration to make more ATP for restoration of the above Use of Anareobic R. defers when the oxygen is consumed to later

VI. Force of Muscle Contraction A. # of Muscle Fibers Recruited 1. Need Stronger Total Stimulus More Action Potentials to More Motor Neurons of Motor Units 2. Frequency of Stimulation a) If more action potentials are sent to the Motor Units per Time, Summation occurs. b) Complete Tetanus will eventually occur = maximum contraction

See previous powerpoint (part B) for a review: “C * See previous powerpoint (part B) for a review: “C. Graded Muscle Responses,” “1. Varying Stimulus Frequency ” and “2. Variation in Stimulation Strength”

3. Size (diameter) of Muscle Fibers a) Large Motor Units have Fibers that are larger Produce the most powerful contractions b) Found mostly in the largest muscles c) Regular Resistance Exercise causes hypertrophy of muscles 4. Degree of Muscle Stretch a) Length-Tension Relationship = As muscle is stretched, the contraction force increases b) Ideal Amount of Stretch—slight: 80-120% of rest length; optimal overlap of thin & thick myofilaments = Longer distance for thin filaments to slide c) Maximal Cross-Bridge Attachment ideal Stretch leads to the most Cross-Bridges formed & strongest contraction Maintained by how muscles attach at Joints Large number Of fibers recruited Large muscle fibers

Contractile force (more cross bridges attached) Figure 9.21 Factors that increase the force of skeletal muscle contraction. High frequency of stimulation (wave summation and tetanus) Large number of muscle fibers recruited Muscle and sarcomere stretched to slightly over 100% of resting length Large muscle fibers Contractile force (more cross bridges attached) © 2013 Pearson Education, Inc.

B. Velocity and Duration of Contraction 2 Major Factors To Classify Muscle Fibers 1. Speed of Contraction: How fast ATPase does “ATP  ADP + P” 2 types general fibers = slow and fast 2. ATP-forming pathways Oxidative fibers – use aerobic pathways: resist fatigue w/ high endurance Glycolytic fibers – use anaerobic glycolysis; high fatigue, low endurance Combine “Slow” and “Fast” with “Oxidative fibers” and “Glycolytic fibers”

3. 3 categories of Fibers and Their Characteristics: slow oxidative fibers fast oxidative fibers (least common) fast glycolytic fibers most muscles have all 3 types a) Speed of Contraction b) Myosin ATPase Activity c) ATP Pathway d) Myoglobin Content e) Glycogen Stores f) Order of Activation Memorize a-c Based on ATP Pathway

Activity best suited for Fiber Diameter Mitochondria 3. 3 categories of Fibers and Their Characteristics … Order of Activation Rate of Fatigue Activity best suited for Fiber Diameter Mitochondria Amount of Capillaries Related to O2 need 4. Load & Recruitment Speed is faster w/out Load 5. Other Factors Genetic Differences Affect of Exercise Based on ATP Pathway

© 2013 Pearson Education, Inc. 3. … Structural and Functional Characteristics of the Three Types of Skeletal Muscle Fibers © 2013 Pearson Education, Inc.

A. Aerobic Exercise–results in an increase of: VII. Response of Skeletal Muscles to Exercise Effects of Aerobic Exercise A. Aerobic Exercise–results in an increase of: Muscle capillaries Number of mitochondria Myoglobin synthesis Occurs mostly in Slow Ox. Possibly: Fast glycolytic fibers become fast oxidative fibers No hypertrophy of muscles Muscle metabolism more efficient Higher Endurance Higher Strength (< than Resistance Exercise) Less Fatigue These Changes are Not Permanent– one must continue the exercise

B. Effects of Resistance Exercise Vigorous Exercise & Isometric Typically anaerobic, results in: Muscle hypertrophy More myofibrils Cells may split into two Significant increase in Strength Increased mitochondria, myofilaments, and glycogen stores Possibly: Fast oxidative fibers converted to fast glycolytic fibers These changes are not permanent Reversibility: Use it or lose it

The Overload Principle State of fitness after adaptation to overload Working muscles = increased muscular strength Muscles adapt to demands Muscles must be overloaded to produce further gains Reversibility: Use it or lose it Increased exercise overload State of fitness after adaptation to overload Exercise overload Current fitness state Fig. 5-3, p. 113

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Availability of Ca2+ in sarcoplasm rises after initial contraction Graded Muscle Responses … Treppe: The Staircase Effect (muscles warm up after long relaxation periods) Treppe – contraction strength increases with time despite same degree of stimulus Availability of Ca2+ in sarcoplasm rises after initial contraction Muscle enzymes more efficient because heat added by prior contractions.

Review Questions Isotonic isometric ____________ contractions change muscle length; ____________ contractions produce tension but no length change. __________ __________ stores phosphates for quick ATP generation. Pyruvic acid is used to make ______ in the aerobic respiration, but is converted to __________ _______ in anaerobic respiration. Creatine phosphate ATP lactic acid Figure 9.20

Review Questions Muscle contractions are precisely controlled by stimulus _____________, the number of action potentials a muscle fiber receives in a given time period, and stimulus __________, the actual number of fibers recruited. Recruitment of fibers usually progresses from __________ to _____________. The stair step effect seen in contraction strength of fully relaxed muscles despite no change in stimulus is known as what? frequency strength smallest biggest Treppe Figure 9.18

Sources of ATP …

QUICK ENERGY SLOW ENERGY For Heavy Exertion For low to moderate Exertion 4-6 s Stored ATP Aerobic Respiration 14-16 s Creatine Phosphate ↓ 30-40 s Anaerobic Glycolysis Aerobic Respiration O2: does not need O2 Requires O2, myoglobin Energy: uses muscle glycogen uses blood glucose and fat # ATP: 2 ATP 32-36 ATP Speed: 2 ½ times faster slow Where in Cell: cytoplasm mitochondria Pyruvic Acid: pyruvic acid  pyruvic acid completely broken lactic acid down Muscle Size: Especially large All sized muscles, especially small Muscles

Participate #4 Slow oxidative _______ _____________ fibers have high endurance and lots of myoglobin. _______ ____________ fibers have fast acting ATPases and rely mainly on aerobic respiration for fuel. _______ _____________ fibers are anaerobic and subject to quick fatigue. Fast oxidative Fast glycolytic

QUICK ENERGY SLOW ENERGY REVIEW QUICK ENERGY SLOW ENERGY For Heavy Exertion For low to moderate Exertion 4-6 s Stored ATP Aerobic Respiration 14-16 s Creatine Phosphate ↓ 30-40 s Anaerobic Glycolysis Aerobic Respiration O2: does not need O2 Requires O2, myoglobin Energy: uses muscle glycogen uses blood glucose and fat # ATP: 2 ATP 32-36 ATP Speed: 2 ½ times faster slow Where in Cell: cytoplasm mitochondria Pyruvic Acid: pyruvic acid  pyruvic acid completely broken lactic acid down Muscle Size: Especially large All sized muscles, especially small Muscles

QUICK ENERGY SLOW ENERGY HANDOUT QUICK ENERGY SLOW ENERGY For Heavy Exertion For low to moderate Exertion 4-6 s Stored ATP Aerobic Respiration 14-16 s Creatine Phosphate ↓ 30-40 s Anaerobic Glycolysis Aerobic Respiration does not need O2 Requires O2, myoglobin uses muscle glycogen uses blood glucose and fat 2 ATP 32-36 ATP 2 ½ times faster slow Cytoplasm Mitochondria Pyruvic Acid  Pyruvic Acid completely broken Lactic Acid down Especially large muslces All sized muscles, especially small

QUICK ENERGY SLOW ENERGY For Heavy Exertion For low to moderate 4-6 s Stored ATP Aerobic Respiration 14-16 s Creatine Phosphate ↓ 30-40 s Anaerobic Glycolysis Aerobic Respiration does not need O2 Requires O2, myoglobin uses muscle glycogen uses blood glucose and fat 2 ATP 32-36 ATP 2 ½ times faster slow cytoplasm mitochondria pyruvic acid  pyruvic acid completely broken lactic acid down Especially large muscles All sized muscles, especially small lg diameter fibers sm diameter fibers, sm motor recruited last units recruited first ADD fast fibers slow fibers & fast fast glycolytic slow oxidative & fast oxidative