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22 Cards in this Set
- Front
- Back
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Myofibril
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-Specialized contractilce elements
-80% of volume of MF -cylindrical intracellular structures 1um in diameter -extend the length of the MF -highly organized cytoskeletal elements (thick/thin) |
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Tropomyosin
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-thin filament
-thread like proteins -lie end-to-end alongside the groove of actin spiral -covers the actin sites that bind with cross bridges=blocking the interaction that=muscle contraction |
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Contractile Proteins
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-actin and myosin> yet neither actually contracts
-binding actin and myosin at cross bridges=energy consuming contraction of the MF |
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Excitation-Contraction coupling
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series of events linking muscle excitation (presence of AP in MF) to muscle contraction (cross-bridge activity=thin filaments to slide closer together to produce sarcomere shortening)
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Sarcomere
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the functional unit of skeletal muscle
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Troponin
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-thin filament
-protein complex -3 polypeptide units 1. one that binds to tropomyosin 2.one that binds to actin 3. one that can bind with Ca2+ *When NOT bound to Ca2+, stabalizes tropomyosin in blocking position over actin's cross bridge binding sites *When bound, shape protein changes, no blocking |
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T Tubules
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-transverse tubule
-formed when surface mem. dips into MF - runs perpendicularly from surface of muscle cell mem into center of MF -AP spreads down into it=rapid transmition of electic activity to center of fiber > AP=permeability changes in sarcoplasmic reticulum |
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Neuromuscular junction
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-at axon terminals when connecting with muscle
-a junction with muscle cells |
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motor unit
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-team of concurrently activated components
-one motor neuron+all MF it innervates -MF that make motor neuron are thoughout whole muscle; simultaneous contraction=evenly distributed (weak) contraction of whole muscle |
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Acetylcholine
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-neurotransmitter
-in excitation-contraction coupling it's released from terminal of motor neuron and initiates an AP in muscle cell that's propagated over entire surface of muscle cell mem. |
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Sarcoplasmic Reticulum
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-modified ER
-network of interconnected compartments surrounding each myofibril (mesh sleeve) -encircles myofibril throughout its length, NOT continuous -segments wrapped around A bands and I bands -lateral sacs store Ca2+ -spread of AP down T tubule triggers release of Ca2+ to cytosol |
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3 forms of muscle
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1. skeletal
2. cardiac 3. smooth *all have specialized contractile apparatus made up of thin actin filaments that slide relative to stationary, thick myosin filaments in response to a rise in cytosolic Ca2+ to accomplish contraction * all directly use ATP |
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Skeletal Muscle
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-striated by a highly organized internal arrangement
-myofibrils -A and I bands -cross bridges -Voluntary muscle |
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Cardiac Muscle
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-Striated
-Involuntary |
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Smooth Muscle
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-Unstriated
-Involuntary |
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Levels of organization in skeletal muscle
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Whole Muscle->MF->myofibril->think and thin filaments->myosin and actin
(organ,cell,specialized intracellular structure, cytoskeletal elements, proteins) |
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Sliding filament theory if muscle contraction
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thin filaments on each side of sarcomere slide inward over stationary thick filaments toward the A band's center. As they slide inward, thin filaments pull Z lines to which they are attached closer together;sarcomere shortens. As all sarcomeres shorten simultaneously, the entire fiber becomes shorter
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Twitch summation
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When the two twitches resulting from the two Ps add together to produce greater tension in the fiber than that produced by a single AP
-similar to temporal summation of EPSPs at the postsynaptic neuron |
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2 primary factors that can be adjusted to accomplish gradation of whole-muscle tension
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1. the number of muscle fibers contracting within a muscle
2. the tension developed by each contracting fiber |
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Tetanus
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-When the muscle fiber is stimulated so rapidly that it doesn't have a change to relax between stimuli
-a smooth, sustained contraction of max strength -2 or 4 times stronger than a single twitch |
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Length-Tension relationship
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p. 272
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Force-Velocity relationship
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p. 275
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