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36 Cards in this Set
- Front
- Back
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Smooth muscle, general |
involuntary slow and weak non-striated wave-like contractions |
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Skeletal muscle, general |
voluntary fast and strong striated |
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Cardiac muscle |
involuntary intermediate speed and strength wave-like contractions striated |
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Thin filaments basic structure |
2 intertwined globular actin filaments that make a helix |
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Thick filaments basic structure |
Myosin II with 4 light and 2 heavy chains two globular heads - ATPase motors myosin tails are anti-parallel so heads on opposite ends (opposite polarity) |
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Filament sliding |
myosin head walks on actin which pulls thin filaments closer together -this action is common amongst all muscle types |
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Organization of smooth muscle filament |
actin randomly arranged project from spherical points (attachment plaques & dense bodies) |
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Organization of striated (cardiac and skeletal) muscles |
actin project from flat disc to create cylindrical filaments (thin) with thick filament in between |
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T or F, Calcium is the signal that triggers contraction in all three muscle types |
True but how it happens varies |
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Calcium signaling in striated muscles |
Ca binds to troponin C (aided by troponin T and I) Change in conformation pushes tropomysoin out exposing myosin binding site overall fast rxn |
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Calcium signaling in smooth muscle |
Ca binds to calmodulin Myosin light chain Kinase (MLCK) activated which phosphorylates light chain tails can assemble into bipolar filament overall slow rxn |
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Histology of smooth muscle |
cells are long and spindle shaped but contraction deforms nucleus into corkscrew shape nuclei are centrally placed Dense bodies are within cytoplasm Attachment plaques beneath plasma membrane are sites for thin filaments Connected via gap junctions (wave-contraction) Desmin intermediate filaments and alpha-actin are actin-anchoring proteins; stabilize the dense bodies and attachment plaques |
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What is special about smooth muscle cells? |
they are regenerative (act as stem cell) |
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Histology of skeletal muscles |
BIG myofiber= muscle cell, multi-nucleated on the periphery Contraction: I band slides over A band (I & H band narrow causing sarcomere to shorten) |
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Sarcomere |
functional unit between two Z-discs |
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Dark bands (A) |
Thick filaments at center of sarcomere |
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Light bands (I) |
thin filaments on either side of sarcomere |
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H zones |
light region in middle of A band |
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Z-disc |
Where the thin filaments are attached; dark line separating sarcomeres |
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M Line |
thin line in center of H zones (stabilizing proteins) |
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Why does the thickness of I band change but not A band? |
the A band is solely measuring the length of the thick filament which doesn't change However when you get contraction, the segment of only thin filament without thick filament decreases because you would get overlapping, thus I band thickness would decrease |
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What happens if you had a mutation in actin and/or myosin? |
embryonic lethal |
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Where can you get mutations in muscles? |
ancillary proteins |
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Ancillary proteins |
Titin: regulates position of thick filaments Nebulin: regulates length of thin filaments Desmin: connect z-disc and keep myofibrils in register Dystrophin/dystroglycan/sarcoglycan: transfers contractile force to ECM via laminin |
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T tubules |
invaginations of the sarcolemma that dive deep to each myofibril depolarization of membrane travels within to go to sarcoplasmic reticulum |
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Sarcoplasmic reticulum |
like an ER surrounds all myofibrils Ca storage |
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Endomysium |
surround individual muscle fibers |
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perimysium |
bundles muscle fibers into fasciles |
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epimysium |
bundles fasicles into muscle t |
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Fast twitch fibers |
Type II white fibers powerful but incapable of anaerobic metabolism fewer mitochondria and red colored oxygen-binding protein fast version of myosin |
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Slow twitch fibers |
Type I red fibers less powerful, endurance fiber can do anaerobic metabolism contain much more myoglobin and mitochondria slower version of myosin |
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What can be modified with exercise? |
mix of fast twitch and slow twitch fibers |
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Myoblast (satellite cells) |
the muscle's stem cell; located in the endomesium can fuse with one another and also their myofiber in order to grow the myofiber in diameter (adaptation: increase in muscle performance in response to need) also mediate regeneration after injury secrete myostatin to limit their own growth |
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How long does restoration of myofiber occur? |
14 days |
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Cardiac muscle |
mono or binucleated, branched, striated nucleus in the center intercalated discs: contains gap junctions (depolarizing), and also adherent junctions (desmosomes and adherens) lots of mitochondria |
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Con of cardiac muscle |
no regenerative capacity -dead myocytes are replaced with connective tissue |
