KIN 3306 1nd Edition Lecture 5 Outline of Last Lecture I Test Information II Extra Credit Information III Top Hat IV Short Answer Question Samples V Essay Question Samples Outline of Current Lecture I Overview II Structure of Muscle III Structure of a Muscle Fiber IV Components of a Muscle Fiber V Components of a Myofibril VI Components of a Sarcomere VII Myosin VIII Actin IX Actin and Myosin Structure X Muscle Contraction XI Phases of Muscle Contraction XII Resting Membrane Potential 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 XIII Action Potential XIV Excitation Contraction Coupling XV Motor Unit XVI Neuromuscular Junction XVII Sliding Filament Theory XVIII Energy for Contraction XIX Muscle Relaxation XX Fiber Type Characteristics XXI Bergstrom Muscle Biopsy Needle XXII Muscle Histochemistry XXIII Fiber Type and Performance XXIV Other Factors Which Influence Muscle Force XXV Force Length Relationship XXVI Muscle Fatigue during Exercise XXVII Summary of Muscle Fibers Current Lecture I Overview a Muscle Contraction b Muscle Fiber Types c Fiber Type and Athletic Performance d Muscle Fatigue during Exercise e Sarcopenia II Structure of Muscle a III Structure of a Muscle Fiber a b Muscle Fiber Muscle Cell c Myofibrils are the smallest pieces IV Components of a Muscle Fiber a Plasmalemma plasma membrane i Attach to tendons ii Folds for stretching iii Junctional folds iv Transport in and out of cell b Sarcoplasm cytosol cytoplasm i Gelatin like substance ii Storage site for glycogen myoglobin and other proteins mineral fats organelles c Transverse Tubules i Run laterally through muscle fiber ii Path for nerve impulses iii Path in and out of muscle fiber d Sarcoplasmic Reticulum i Runs parallel to muscle fiber ii Calcium storage V Components of a Myofibril a b We can break down myofibrils into sarcomeres The sarcomere is what is physically contracting to allow our muscles to contract VI Components of a Sarcomere a Sarcomere basic contractile unit of a myofibril i I Band ii A Band iii H Zone iv M Line v Z Disc b Sarcomere includes two types of protein filaments i Thick Filament Myosin ii Thin Filament Actin c Alignment of the thick and thin filaments is what give muscle its striations VII Myosin a Comprises 2 3 of skeletal muscle protein b Two protein strands twisted together c Globular heads myosin crossbridges d Titin filaments stabilize myosin i Titin is the light line that connects to the z disc Titin is not considered to be a part of the thick filament but after the muscle contracts titin will put everything back in starting position to maintain the resting position VIII Actin a Thin filaments are composed of 3 proteins i Actin globular proteins form strands ii Tropomyosin twists around actin strand iii Troponin bound at intervals to actin b Anchored to Z Disk c d Tropomyosin s purpose is to block myosin binding sites on actin This way in resting conditions myosin cant bind e When Ca2 is bound to troponin it will then move Tropomyosin IX Actin and Myosin Structure a X Muscle Contraction a Muscles are divided into motor units comprised of i Alpha motor neuron ii Muscle fibers b In summary Muscle contraction begins with a neural impulse Muscles are voluntary All of our muscles are divided into motor units one motor neuron that touches innervates several muscle fibers XI Phases of Muscle Contraction a Action Potential Calcium Release b Calcium Troponin Binding Tropomyosin Shif c Actin Myosin Binding d Myosin Power Stroke ATP Binding e In summary AP leads to calcium release Troponin moves Tropomyosin so actin and myosin can bind The power stroke is the movement of myosin to contract the sarcomere Then ATP is used to fuel muscle contraction XII Resting Membrane Potential a RMP 70mV b Caused by uneven separation of charged ions inside K and outside Na the cell c More ions outside the cell than inside d Membrane more permeable to K e Sodium Potassium Pumps maintain imbalance i 3 Na out ii 2 K in f In summary AP is an electrical nerve impulse The RMP is the charge of a muscle fiber cell at rest The reason it has a charge is because of the ion distribution There are less ions inside the cell versus outside of the cell The ions we re talking about are K and Na To maintain this negative charge of 70mV we have a Na K pump K leaks a little bit in and out of the cell An AP is a disruption of this resting charge that propagates an electrical impulse into the cell XIII Action Potential a b In summary The initial stimulus comes from neurotransmitters in muscles the neurotransmitter is Ach This stimulus initiates the AP Repolarization is when K runs out In the dip after 7 this is called hyperpolarization because the K gates are not tightly regulated so they stay open a little longer than they need to so K will get out a bit more c In summary AP is always the same magnitude What can make AP strong or less strong is summation and recruitment Summation is if you have several AP happening quick all of them work together and generate one big contraction Recruitment is where more muscle fibers are recruited and so more motor units are recruited d Make sure to know what is happening at each phase and what an AP is doing TQ XIV Excitation Contraction Coupling a Action potential travels to sarcoplasmic reticulum causes release of calcium into sarcoplasm b Calcium binds to troponin on thin filament c Troponin moves Tropomyosin revealing myosin binding sites on actin d Myosin cross bridges bind to actin e In summary AP goes into the T Tubules and so this is when we get the initiation of the muscle contraction Once the AP comes through the SR releases calcium so calcium will be freely available XV Motor Unit a XVI Neuromuscular Junction a b In summary They do not actually touch The neuron sits in a fold within the plasmalemma As AP goes down there is a neurotransmitter that carries the signal from the neuron to the muscle fiber since they re not physically touching As it gets to the end the neurotransmitter is released into the space synaptic cleft the Ach binds to plasmalemma and this is the initial signal that starts the AP so it can get over the 55 threshold c In summary It goes from electrical signal chemical signal then reinitiates the electrical signal that then goes into the muscle fiber XVII Sliding Filament Theory a Muscle contraction muscle fiber shortening b Myosin power stroke i Myosin