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Skel. Muscle Tissue
Zoo141 (Uno) Study Guide
| Term | Definition |
|---|---|
| Epimysium | dense layer of collagen fibers surrounding entire skeletal muscle |
| Perimysium | fibrous layer that divides the skeletal muscle into fascicles (bundles of skeletal muscle fibers |
| Endomysium | delicate connective tissue surrounding individual muscle fibers |
| Tendon | bundle of collagenous connective tissue attaching muscle to bone |
| Aponeurosis | broad sheet of collagenous connective tissue attaching muscle to bone |
| Development of skeletal muscle fibers | myoblasts fuse into large multinucleate cells, which differentiate into skeletal muscle fibers (some myoblasts remain undifferentiated, as myosatellite cells) |
| Sarcolemma | plasma membrane |
| Sarcoplasm | cytoplasm |
| Myofibrils | bundles of protein filaments called myofilaments, which contain repeating functional unit called sarcomeres a. thin filaments: composed primarily of actin b. thick filaments: composed primarily of myosin |
| Transverse tubules (T tubules) | carry electrical activity from sarcolemma into cell interior |
| Sarcoplasmic reticulum (SR) | -carry electrical activity from sarcolemma into cell interior -stores and releases calcium, to start muscle contraction a. terminal cisternae = expanded chambers that contact T tubule, forming triad |
| A band | contains the entire width of the thick filaments |
| H band | contains the part of the thick filaments that does not overlap the thin filaments |
| I band | contains the part of the thin filaments that does not overlap the thick filaments |
| M line | connect the central portion of each thick filament |
| Z line | marks boundary between adjacent sarcomeres; consists of actinin proteins |
| G-actin (globular actin) | contains active sites that bind to myosin |
| F-actin (filamentous actin) | twisted strand composed of two rows of G-actin molecules |
| Nebulin | holds the F-actin strand together |
| Tropomyosin | strands that cover the active sites on G-actin |
| Troponin | has three subunits, that bind to tropomyosin, G-actin, and calcium |
| Myosin | has head that binds to thin filaments, and tail |
| Titin | forms core of thick filament |
| Structure of Neuromuscular | intercellular connection between muscle fiber and neuron |
| Synaptic Terminal of Neuron | contains vesicles filled with Ach |
| Motor End Plate of Muscle Fiber | has deep creases called junctional folds |
| Synaptic Cleft | space containing AChE (enzyme that breaks down ACh) |
| Latent Period | action potential sweeps across sarcolemma, SR releases Ca ions |
| Contraction Phase | tension rises to peak, as cross-bridge interactions occur |
| Relaxation Phase | tension decreases, as Ca levels fall, tropomyosin covers the active sites on actin, and myosin is blocked from binding to actin |
| Motor Unit | all the muscle fibers controlled by a single motor neuron |
| Isometric Contraction | muscle contraction without change in length |
| Isotonic contraction | muscle length changes during contraction a. concentric contraction: muscle shortens during contraction b. eccentric contraction: muscle lengthens during contraction |
| Sources of energy stored in a typical muscle fiber | 1. ATP 2. Creatine Phosphate (CP) 3. Glycogen |
| ATP production in resting muscle | 1. more than enough oxygen available for mitochondria 2. primary energy sources: glucose and fatty acids from blood enter mitochondria 3. surplus of ATP used to convert creatine to creatine phosphate, and glucose to glycogen |
| ATP production in muscle at peak activity levels | 1. not enough oxygen available for mitochondria 2. primary energy sources: glucose from stored glycogen -> glycolysis (lactic acid also produced) |
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