Examples of sarcomere in the following topics:
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- Intercalated disks transmit electrical action potentials between sarcomeres.
- A sarcomere is the basic unit of muscle tissue in both cardiac and skeletal muscle.
- Sarcomeres appear under the microscope as striations, with alternating dark and light bands.
- Sarcomeres are connected to a plasma membrane, called a sarcolemma, by T-tubules, which speed up the rate of depolarization within the sarcomere.
- Actin molecules are bound to the Z-disc, which forms the borders of the sarcomere.
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- Muscles exist in this state to optimize the force produced
during contraction, which is modulated by the interlaced myofilaments of the sarcomere.
- When a sarcomere contracts, myosin heads attach to actin to form cross-bridges.
- This results in sarcomere shortening, creating the tension
of the muscle contraction.
- If a sarcomere is stretched too far, there will
be insufficient overlap of the myofilaments and the less force will be produced.
- In mammals, there is a strong overlap between the optimum and actual resting length of sarcomeres.
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- Previously attributed to the accumulation of lactic acid during exercise, it is now understood that DOMS is due to structural damage in sarcomeres, particularly to the z-disks and contractile filaments.
- Damage to the sarcomeres causes aninflux of white blood cells, leading to inflammation, which is itself associated with increased plasma enzyme concentration, myoglobinemia, and abnormal muscle structure and histology.
- A further response to sarcomere damage is necrosis following damage to the mysium, which peaks about 48 hours following exercise.
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- Schematic of filament arrangement in normal, functional sarcomeres, versus atophied sarcomeres following 17-day space flight
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- Cross-bridge cycling occurs, shortening the sarcomere, muscle fiber, and muscle.
- Cross-bridge cycling occurs even though the sarcomere, muscle fiber, and muscle are lengthening, controlling the extension of the muscle.
- In both instances, cross-bridge cycling is maintaining tension in the muscle; the sarcomere, muscle fibers, and muscle are not changing length.
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- Cardiac muscle, like skeletal muscle, is comprised of sarcomeres, the basic, contractile units of muscle.
- Sarcomeres are composed of long, fibrous proteins that slide past each other when the muscles contract and relax.
- Two of the important proteins found in sarcomeres are myosin, which forms the thick filament, and actin, which forms the thin filament.
- The tissue structure of cardiac muscle contains sarcomeres that are made of myofibrils with intercalated disks, that contain cardiomyocytes and have many mitocondria.
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- As the action potential travels between sarcomeres, it activates the calcium channels in the T-tubules, resulting in an influx of calcium ions into the cardiomyocyte.
- The myosin head binds to ATP and pulls the actin filaments toward the center of the sarcomere, contracting the muscle.
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- Physiologically, rigor mortis is caused a release of calcium facilitating crossbridges in the sarcomeres; the coupling between myosin and actin cannot be broken, creating a constant state of muscle contraction until enzymatic decomposition eventually removes the crossbridges.
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- This leads to disruptions of mechanical stabilization and calcium concentration regulation within the sarcomeres, altering the ability of filaments to bind and cause contraction.
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- This is because sarcomeres are stretched further when EDV increases, allowing the heart to eject more blood and keep the same ESV if no other factors change.