KIN 3306 1nd Edition Exam 2 Study Guide Lectures 5 7 Lecture 5 March 3 The Structure of a Muscle Fiber Muscle Cell The Components of a Muscle Fiber The plasmalemma attaches to tendons folds for stretching has junctional folds and transports in and out of the cell The sarcoplasm is a gelatin like substance that is the storage site for glycogen myoglobin and other proteins minerals fats organelles The transverse tubules run laterally through the muscle fiber and are the path for nerve impulses The sarcoplasmic reticulum runs parallel to the muscle fiber and is where calcium is stored The Components of a Myofibril We can break down myofibrils into sarcomeres The sarcomere is what is physically contracting to allow our muscles to contract The Components of a Sarcomere The sarcomere is the basic contractile unit of a myofibril and consists of the I band Aband H zone M line and Z disc and includes two types of protein filaments myosin thick and actin thin Myosin compromises 2 3 of skeletal muscle protein and has globular heads that form cross bridges The titin filaments stabilize myosin by putting everything back into starting position after contraction Actin has Tropomyosin that wraps around actin and Troponin that is bound at intervals to actin and Actin is anchored to the Z disks The purpose of Tropomyosin is to block myosin binding sites on actin When calcium is bound to troponin it will then move Tropomyosin Muscle Contraction begins with a neural impulse Muscles are also voluntary Our muscles are divided into motor units and one motor neuron innervates several muscle fibers The phases of muscle contraction are listed below What happens is that AP leads to calcium release then troponin moves tropomyosin so actin and myosin can bind the power stroke occurs which is the movement of myosin to contract the sarcomere and then ATP is used to fuel muscle contraction Action potential calcium release Calcium troponin binding tropomyosin shift Actin myosin binding Myosin power stroke ATP binding The Resting Membrane Potential is 70 mV It is caused by an uneven separation of charged ions inside and outside of the cell There are less ions inside the cell versus outside of the cell To maintain the negative charge of 70 mV we have a Na K pump An AP is a disruption of this resting charge that propagates an electrical impulse into the cell Action Potential The initial stimulus comes from neurotransmitters such as Ach This stimulus initiates the AP Repolarization is when K runs out In the dip after 7 this stage is called Hyperpolarization where the K gates are not tightly regulated so they stay open a little bit longer than they need to be opened so K will leak a bit more AP is always the same magnitude What can make AP strong or less strong is summation and recruitment Neuromuscular Junction The neuron and the muscle do not actually touch The neuron sits in a fold within the plasmalemma and as AP goes down into the junction there is a neurotransmitter that carries the signal from the neuron to the muscle fiber As it gets to the end the neurotransmitter is released into the space synaptic cleft the Ach binds to the plasmalemma and this is the initial signal that starts the AP so it can get over the 55 threshold It goes from electrical signal chemical signal then reinitiates the electrical signal that then goes into the muscle fiber Energy for Contraction The ATP binding sites are on the myosin head ATPase on the myosin head splits into ADP and Pi The energy released fuels the tilting of the myosin head which is the power stroke Additional ATP is required to keep the contraction going ATP allows myosin to reach forward and grab actin Myosin can either be bound to actin or ATP but not to both Muscle Relaxation The calcium pumps return calcium to the SR where it is stored for future use Calcium availability is important because the lack of calcium will result in fatigue where you cannot contract anymore Muscle Fiber Type Characteristics Type 1 Fibers are slow twitch slow oxidative and are associated with the color white o Distance runners triathletes cyclists Type2 Fibers are fast twitch o Sprinters weight lifters hockey players Factors that Influence Muscle Force Number of motor units activated Type of motor units activated Muscle size Initial muscle length Joint angle Speed of muscle action Muscle Fatigue during Exercise If short term fatigue is going to come from acidity The acid denatures proteins and stops proteins from functioning If long term fatigue is related to a lack of calcium Lecture 6 March 10 Resistance Training is the only exercise mode that the body can adapt to with only a single exposure 6 months of resistance training can increase strength up to 100 Muscle Strength maximal force that a muscle can generate Muscle Power measure of how quickly one can move a fixed force Muscle Endurance ability to maintain a near maximal muscle force General Training Principles include individuality specificity reversibility progressive overload and variation In order to make improvements and strength gains one has to continue to overload oneself by constantly increasing weights or pace to continue to see progress Periodization is a cycle that athletes typically go through and is made up different cycles a macrocycle mesocycle microcycle It is also made up of different periods a preparatory first transition competition period and second transition period Macrocycle an entire training year the whole periodization cycle Mesocycle two or more cycles within a macrocycle Microcycle typically one week long but it depends on the program Resistance Training Program Design Must to consider the athlete s specific sport or event or goals the exercise movements should be specific to the athlete Must consider the major muscle groups the large muscles are normally trained before the smaller muscles Must consider the type of training for the desired outcome the number of sets resistance repetitions and velocity should be considered Must consider injury prevention the athlete must have adequate rest Strength Training Exercise Categories Isometric Static muscle is at constant length and is anything that you hold o Ex plank Isotonic Dynamic a constant load where you have the eccentric and concentric phases o Ex bicep curl Isokinetic constant speed the load is variable but the speed of contraction is the same o Ex biodex Phases of Strength Gains has two phases Neural Adaptation is the first place where you get your