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| skeletal, cardiac, smooth |
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| are long, tiny fibers that are bundled into somewhat bigger fibers. These bigger fibers will group together to make a muscle |
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| Every muscle fiber is formed from fused _______ that turn into _________ |
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| Muscle fibers have multiple |
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| Each myofibril is made up of _____ which are arranged end to end. |
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| Sarcomeres are made up of ____ and ____ filaments |
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| Sarcomeres were discovered through |
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| some bands move and others dont |
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| Four parts of a myofibril |
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| Thin filaments extend from |
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| Actin myofilaments are made up of |
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| In thick myofilaments, myosin is organized into _(#)__ protein subunits. Each complex has a long, thin tail made of two supercoiled ________ segments of two myosin heavy chains. At one end are two heads, which belong to a myosin ____ chain. In addition, ____ myosin light chains and ____ regulatory light chains associate with the heads. |
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| Proteolytic enzymes _____ and _____ cleave myosin complexes at particular locations |
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| Trypsin cleaves myosin into two pieces: |
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light meromyosin
heavy meromyosin |
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| Light meromyosin contains |
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| Heavy meromyosin contains |
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| head and light myosin chains |
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| Papain cleaves heavy meromyosin into three pieces: |
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| Myosin complexes will polymerize spontaneously in vitro to reconstitute ____ filaments with an organization identical to those found in muscle. |
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| Myosin complexes join the thick filament with their tails |
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| Myosin complexes will polymerize spontaneously in vitro to reconstitute ____ filaments with an organization identical to those found in muscle. |
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| Myosin complexes join the thick filament with their tails |
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| sarcomeres shorten when actin and myosin filaments move past each other |
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| The tension produced by the muscle is maximal when |
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| the overlap between thick and thin filaments allows for the largest number of myosin cross bridges to bind to actin |
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| Two reasons why tension decreases with increased length |
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1. Less overlap, less cross-bridges
2. Thin filaments begin to collide with each other |
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-the length of the muscle doesn't change
-Tension increases and decreases |
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-muscle is allowed to shorten during tension generation
-tension being generated is constant
-brief dynamic period when the muscle returns to rest |
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| What are responsible for graded muscle contractions |
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| At the minimum contraction, has |
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| one motor neuron and one muscle fiber |
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| The larger the motor unit, the greater the |
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| Free calcium ions in the cytosol regulate |
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| the state of muscle contraction |
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Glycerin-extracted muscle fibers generate tension when....
They relax when.... |
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-they are exposed to Ca and ATP
-Ca is removed, even if ATP is still present |
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| The force generated by a skinned muscle fiber varies with the |
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| concentration of Ca in the surrounding medium. Force increases with increasing Ca, up to 10-6 M |
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| Function of tropomyosin and troponin |
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| regulate binding between myosin cross bridges and actin thin filaments |
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| binds to actin and blocks myosin binding sites |
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| binds to actin and troponin C |
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In the absence of Ca, troponin T binds to ______ and troponin I binds to _____.
Both troponin I and T bind to |
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tropomyosin
actin
troponin C |
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| When troponin C binds to Ca, its bond to troponin I becomes _____ and the bond between tropinin I and actin is ______. |
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| Both Ca and ATP are required for muscles to |
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| Relaxation only occurs when |
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| ATP is present and Ca is not |
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| Muscle fibers contract when a _______ potential at the _______ _______ causes a _______ action potential in the fiber |
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postsynaptic
neuromuscular junction
propogated |
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| An action potential in the motor neuron causes an ______ ______ potential in the muscle fiber which gives rise to a _______ muscle AP |
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excitatory postsynaptic
propagated |
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| transient, all or none contraction |
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| The threshold for potential contraction |
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| Electrotonic transmission |
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| causes a large depolarization that spontaneously moves from the point |
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| Behavior of a muscle fiber |
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| extensions of the plasma membrane that reach deep into the interior of each muscle fiber. Associated with the sarcoplasmic reticulum |
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| The process of spreading an AP along the entire length of a muscle fiber involves |
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| The process of spreading Ca2+ throughout entire sarcoplasm of a muscle fiber involves the |
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| The concentration of free Ca in a muscle fiber can be measured using |
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| Tension only rises after (in relation to Ca) |
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| Ap is over and intracellular Ca has begun to decline |
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| The release of Ca2+ is due to the interaction of two membrane proteins: |
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| ryanodine and dihydropyridine receptors |
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| Dihydropyridine receptors span __ ______ and come in clusters of __. Each receptor associates closely with the extracellular foot of a ________ receptor, which extends from the ____ membrane. |
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| _______ inside the SR binds to Ca |
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| Near the Z disks in mammals and amphibian skeletal muscle, T tubules at the terminal _____ from two sarcomeres form _____. |
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| Feet connect terminal cisternae with __ ______ in each triad. |
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Ca concentration:
Voltage sensitive ________ receptors and ryanodine receptors work together. linking the depolarization of the T tubules to the opening of the ____ channels in the ____ membrane. A ____ ATPase in the SR membrane requesters Ca from the _______, and the calsequestrin inside the SR bind ___. This reduces the amount of free ionic ___ inside the SR. |
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dihydropyridine
Ca
SR
myoplasm
Ca
Ca |
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| = sarcoplasm = cytoplasm of the muscle fiber |
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| One of the lowest concentration intracellular ions |
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| Ryanodine receptor is a ________ gated Ca channel – opens when the other opens, causes the physical change |
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| The quickest twitch muscles we have are associated with our |
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| Muscle fibers can gerenate ATP ________ – fermentation. The product is |
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| protein that acts as a cellular store for phosphate |
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| Three ways to generate ATP |
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Fast twitch fibers generally use glycolysis and fermentation, so do not rely on oxygen
Slow twitch fibers rely on oxidative phosphorylation – can generate a lot of ATP |
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| Lactate should be high in |
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| fast twitch because use fermentation |
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