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Bio Ch. 44
| Term | Definition |
|---|---|
| Myofibrils | Strands which make up muscle cells |
| Sarcomeres | Contractile units of myofibril composed of actin and myosin |
| Myofiber | Muscle cell |
| Myocyte | Muscle cell |
| Muscle cell (nucleus, excitability - 2) | multi-nucleated, can be excited by membrane depolarization, stimulated by PNS by NMJ |
| T/F - Muscle contraction requires large amounts of energy under the form of ATP | True |
| Myofiber nucleus placement | peripherally |
| striations | repeating sarcomeres - bands or stripes perpendicular to long axis |
| connective tissue | material between fiber bundles |
| nerve location | surround outside of muscle |
| Thin filament | actin, troponin, tropomyosin |
| Thick filament | myosin |
| Myosin pulls or pushes on actin? | pulls |
| A band | unchanged |
| I band | reduced |
| H zone | reduced |
| M line | bisects sarcomere unit |
| Z line | either end of sarcomere unit |
| Troponin | red circles |
| Tropomyosin | white stripes |
| Roles of ATP | 1) detachment 2) ATP hydrolysis (energy for a new cycle) |
| cross-bridge cycle | sequence of events from when cross-bridge binds to a thin filament to when it is set to repeat the process |
| Four stages of cross-bridge cycling | binding, power stroke, detaching, resetting |
| Muscle contraction is dependent on this ion | Ca 2+ |
| Cross-bridge cycling - binding: | when Ca 2+ levels are high, cross-bridge can bind to actin - ADP + Pi are already bound to the cross-bridge |
| Cross-bridge cycling - power stroke: | release of Pi, cross-bridge moves toward H zone of sarcomere, "power stroke" moves actin toward H zone, ADP released |
| Cross-bridge cycling - detaching: | ATP binds to myosin, cross-bridge detaches from actin filament |
| Cross-bridge cycling - resetting: | ATP hydrolysis to ADP + Pi - provides energy, cross-bridge moves away from H zone. ADP & Pi remain bound to cross-bridge - cycle begins again |
| fast fibers (ATPase activity) | myosin with high ATPase activity |
| slow fibers (ATPase activity) | myosin with a lower ATPase activity |
| both fibers (strength of force & speed) | maximal force the same with variable speed (fine-tuning is possible) |
| Type I fibers (fiber, force, diameter) | slow fibers, sustained forces needed, smaller diameter |
| Type II fibers (fiber, force diameter) | fast fibers, fast contractions needed, larger diameter |
| dark red fibers | oxidative fibers |
| white fibers | glycolytic fibers |
| fibers w numerous mitochondria for oxidative phosphorylation (ATP production) | oxidative fibers |
| fibers where blood flow is important | oxidative fibers |
| fibers with large amounts of myoglobin (red) | oxidative fibers |
| fibers w numerous glycolytic enzymes & rely on anaerobic glycolysis for ATP production | glycolytic fibers |
| fibers with large stores of glycogen | glycolytic fibers |
| fibers w large store of glycogen | glycolytic fibers |
| glycolytic fibers small or large amounts of myoglobin | small |
| ex - duck breast | oxidative fibers |
| ex - chicken breast | glycolytic fibers |
| 3 major types of muscle fibers | fast-oxidative, slow-oxydative, fast-glycolytic |
| Fast-oxidative fibers structure & function | (high ATPase, high myoglobin/O2)= type IIa : suited for both sustained and rapid actions (intermediate resistance to fatigue) |
| Slow-oxidative fibers structure & function | (low ATPase, high myoglobin/O2)= type I : used for prolonged, regular activity |
| Fast-glycolytic fibers structure & function | (high ATPase, low myoglobin/O2) = type IIb : Very rapid, intense actions but fatigues quickly |
| Aerobic exercise fibers | slow-oxidative & small diameter |
| Anaerobic exercise fibers | fast-glycolytic & large diameter |
| Where does Ca2+ needed for muscle contraction come from? (4) | 1)action potential along plasma membrane down transverse tubules 2)depolarization occurs, Ca2+ channels in sarcoplasmic reticulum open up, Ca2+ diffuses into cell cytosol, 3) binding 4) Ca2+ pumped back into sarcoplasmic reticulum by ATP ion pumps (relax) |
| motor unit | motor neuron end plate + multiple muscle fibers |
| excitation-transduction coupling | neuronal impulse transduced via action potential & converted into intracellular chemical signal (triggers contraction) |
| Increase in the size of muscle fibers [Bone apposition and quality increased] | |
| Muscle Atrophy | Reduction in muscle size [Bone loss] |
| muscle hypertrophy synonym | exercise |
| muscle atrophy synonym | immobilization |
| myasthenia gravis | antibodies, inactivate ACh receptors on skeletal muscles, autoimmune disease |
| Muscular dystrophy (Duchenne) | Abnormal conduction of nerve impulse - lack of dystrophin protein which maintains integrity of muscle plasma membrane, genetic sex-linked recessive, cells swell up and die |
Created by:
pranita_m
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