Muscle & Movement PHSL 3051 Pre Class 12 PDF

Muscle & Movement PHSL 3051 Dr. Barnett Energy Metabolism and Muscle Fiber Types Pre Class 12 Learning Objectives Class 12: Molecular Mechanisms of Contraction and Metabolism Derrickson (1st edition: p. 383-393, 2nd edition: p 394-407) 1. List the energy sources for muscle co...

Muscle & Movement PHSL 3051 Dr. Barnett Energy Metabolism and Muscle Fiber Types Pre Class 12 Learning Objectives Class 12: Molecular Mechanisms of Contraction and Metabolism Derrickson (1st edition: p. 383-393, 2nd edition: p 394-407) 1. List the energy sources for muscle contraction and rank the sources with respect to their relative speed and capacity to supply ATP for contraction. 2. Construct a table of structural, enzymatic, and functional features of fast- glycolytic, fast-oxidative, and slow-oxidative fiber types from skeletal muscle. 3. List the factors that can contribute to muscle fatigue and describe basis of the differences in fatigue resistance in different muscle fiber types. 4. Define a motor unit and describe the order of recruitment of motor units during skeletal muscle contractions producing low, moderate and high amounts of tension. 5. List the factors that determine the tension developed in a whole muscle and explain how each contributes to the amount of tension generated. 2 3 ATP Production in Skeletal Muscle H2N N ATP N N N O O O O -O O O P O P P O- O- O- Kinases OH OH Myosin ATPase Glycolysis Adenosine Triphosphate Ca2+-ATPase Oxidative Phosphorylation Na+/K+-ATPase H2N O Phosphate N -O P O- N O- Energy Energy N N O O O -O P O P O ADP For cellular From food O- O- Sugars OH OH work Fats Proteins Adenosine Diphosphate  ATP production in skeletal muscle 1. Creatine Kinase  One step reaction (fast)  Transfers phosphate from Creatine-phosphate to ADP to regenerate ATP  Limited capacity 2 2. Glycolysis 1 Creatine Kinase  Multistep reaction  Anaerobic  Converts 1 Glucose to 2 ATP 3 3. Oxidative Phosphorylation  Multistep reaction  Requires Oxygen (O2) and mitochondria  Converts 1 Glucose to 36 ATP  Converts Fatty acids to ATP  Converts Amino acids to ATP 4  Muscle Fiber Types Classified according to: Their maximal velocity of shortening (i.e. how quickly myosin can hydrolyze ATP) The major pathway they use to form ATP 1. Slow-oxidative Red muscle, small diameter cells - Slow myosin aerobic metabolism 2. Fast-oxidative Red muscle, intermediate diameter cells - Fast myosin, aerobic and anaerobic metabolism 3. Fast-glycolytic White muscle, large diameter cells - anaerobic metabolism  Motor Units A motor unit is defined as a motor neuron and the population of muscle fibers it innervates. Two motor units can generate more tension than one. When a large amount of tension needs to be generated, more motor neurons (and hence muscle fibers) are recruited.  Recruitment Increasing load Increasing muscle force required Large motor units Small motor units Medium motor units Increasing motor unit size Based on Figure 11.17  Recruitment Motor unit 1: slow-oxidative fibers Motor unit 1: slow oxidative - small diameter muscle fibers - few fibers per motor unit - generates least tension Motor unit 2: fast-oxidative fibers Motor unit 3: fast-glycolytic fibers Motor unit 2: fast oxidative - midsized muscle fibers - moderate # of fibers per motor unit Whole-muscle tension - generates moderate tension Motor unit 3: fast glycolytic - large muscle fibers - many fibers per motor unit - generates most tension, quickly Time Motor unit Motor unit Motor unit 1 recruited 2 recruited 3 recruited