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Ex Phys ch 8
Skeletal Muscle: Structure and Function
| Question | Answer |
|---|---|
| Human body contains how many skeletal muscles? | over 400; which constitute 40-50% of total body weight |
| 3 Functions that Skeletal Muscle perform: | 1) Force generation for locomotion and breathing 2) force generation for postural support 3) heat production during periods of cold stress |
| Muscles attach to bone via... | tendons! |
| origin of muscle- | one end of muscle attached to bone that does not move |
| insertion point of muscle- | opposite muscle fixed to a bone that moves during muscle contraction |
| muscles that decrease joint angle are | flexors |
| muscles that increase joint angle are | extensors |
| epimysium | surrounds entire muscle |
| perimysium | surrounds individual bundles of muscle fibers |
| endomysium | connective tissue around each individual muscle fiber |
| basement membrane | just below endomysium, surrounding each muscle fiber- extra layer of protective tissue |
| sarcolemma | cell membrane surrounding muscle fiber cell |
| satellite cells | play role in muscle growth and repair, contribute to muscle growth during strength training |
| myonuclear division | cytoplasm surrounding each nucleus |
| more nuclei allow for.. | greater protein synthesis |
| myofibrils | contain contractile proteins actin (thin) and myosin (thick) |
| a sarcomere includes.. | Z line, M line, H zone, A band, I band |
| Sarcoplasmic reticulum (SR) | storage sites for calcium |
| transverse tubules extend from | sarcolemma ---> SR |
| motor unit- | the motor unit and the muscle fibers it innervates |
| neuromuscular junction | junction between motor neuron and muscle fiber |
| motor end plate | pocket formed around motor neuron by sarcolemma |
| neuromuscular cleft- | short gap between neuron and muscle fiber |
| acetylcholine being released from a motor neuron causes what.. | EPP- End Plate Potential |
| EPP is ALWAYS.. | large enough to exceed threshold and is signal to begin contractile process |
| The Sliding Filament Model | best explains the process of muscular contraction; andrew huxley and colleagues, actin and myosin interaction |
| First step of The General Process of Muscular Contraction | Myofilaments actin and myosin do not change length during muscle contraction |
| Second step of Muscular contraction | during contraction, actin myofilaments at each end of the sarcomere slide past the myosin filaments toward each other. Z discs become closer together as the sarcomere shortens. |
| Third step of Muscular contraction | As actin myofilaments slide over the myosin myofilaments, the H zones and I bands narrow. The A bands stay the same, they do NOT narrow. |
| Fourth step of muscular contraction | In a fully contracted muscle, the ends of the actin myofilaments overlap and the H zone disappears. |
| 3 Sources of ATP production in muscle contraction: | 1) phosphocreatine 2) glycolysis 3) oxidative phosphorylation |
| Excitation-Contracting coupling | sequence of events in which a nerve impulse (AP) reaches the muscle membrane and leads to shortening by cross-bridge activity |
| breakdown of ATP for contraction energy is by what enzyme?? | myosin ATPase (located of head of myosin cross-bridges) |
| power stroke | a single contraction cycle |
| when muscles are relaxed... | actin and myosin have a weak binding state |
| The 2 Regulatory Proteins which Control Muscular contraction (regulate interaction between actin and myosin) | troponin and tropomyosin |
| where are troponin and tropomyosin located? | on the actin molecule |
| in relaxed muscle, which protein blocks the active sites on actin molecules where myosin cross-bridges must attach? | tropomyosin |
| what is released from the SR that diffuses into muscles to bind to troponin? | Calcium |
| What is the trigger step in the detailed outline of muscular contraction? | When the AP reaches the SR and calcium is released and diffuses into the muscle to bind to the protein troponin. |
| The trigger for contraction to occur is linked to release of stored Ca++ from where? | lateral sac aka terminal cisternae of SR |
| In a resting (relaxed) muscle, the concentration of Ca++ is .. | very low |
| The contraction cycle can be repeated as long as... | there is free Ca++ available to bind to troponin and ATP can be hydrolized to provide the energy |
| what is muscle fatigue? | decline in muscle power output, decrease in force generation, decrease in shortening velocity |
| what causes muscle fatigue? | build up of hydrogen, lactic acid, high intensity, accumulation of ADP + Pi and free radicals, long duration exercises (2-4 hrs), disturbances in muscle/ extracellular electrolyte homeostasis |
| what are muscle cramps? | spasmodic, involuntary muscle contraction |
| what causes muscle cramps? | electrolyte depletion and dehydration theory |
Created by:
sbush0804
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