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Explain how a skeletal muscle contracts and relaxes?
Contraction:Calcium ion (from sarcoplasmic reticulum) binds to troponin of actin filament.Re-orientation occurs in actin filament allowing it to bind to the myosin filament.Globular head of myosin filament binds to actin filament.Myosin filament splits an ATP molecule and as result it bends causing actin filament (attached to it) to slide over it. When the overlap of actin and myosin filament is maximum, filaments will occupy less space thus muscle is in contracted state.Relaxation:ATP binds to myosin filament and myosin returns to its original position (relaxed state).Sarcoplasmic reticulum re-accumulates the calsium ion by active transport. As the result actin filament is dettached from myosin filament.When the overlap of myofibrils is minimal, muscle will be in relaxed state.
What do muscle fibers need to reset the myosin heads?
ATP binds myosin, allowing it to release actin and be in the weak binding state (a lack of ATP makes this step impossible, resulting in the rigor state characteristic of rigor mortis). The myosin then hydrolyzes the ATP and uses the energy to move into the "cocked back" conformation.
What binds skeletal muscle and the tough translucent sheath?
Fascicles
What are the proteins are involved in muscle contraction?
Actin and myosin
What is the next step in muscle contraction after the actin changes shape?
Actin Changes ShapeApexMyosin binds to ActinAPEX
What function do calcium ions perform during skeletal muscle contractions?
During skeletal muscle contraction calcium ions expose myosin binding sites on to the actin. When a nerve sends a signal to a muscle to do some "action" the release of acetylcholine at the neuromuscular junction triggers calcium to be released into the cytoplasm. At rest, the cell has a low concentration of calcium. When the calcium concentration rises, calcium diffuses over to the muscle protein fibers and causes a conformational change. Calcium binds to the troponin and causes it to rotate slightly which forms a crossbridge that drags along the actin fiber and shortens it thus creating muscle fiber contraction.
Which molecule binds to the myosin head in order to break the actin-myosin bond?
ATP
What are overlapping patterns of actin and myosin called?
binds
What is perimysium?
Perimysium is the connective tissue that binds muscle fibers into groups. The muscles will be grouped in bundles of 10 to 100.
What is the role of atp in muscle concentration?
Atp plays a critical role in muscle. Breaking of the cross-bridge is possible only if atp binds to myosin, thereby allowing it to be free for the following contraction.
What binds calcium ions in a smooth muscle causing contraction?
Contractions are initiated by the calcium-activated phosphorylation of myosin rather than calcium binding to troponin.
How is calcium used in muscle contraction?
Calcium binds to troponin, which moves the tropomyosin out of the way so that myosin can bind to actin; this ultimately causes a power-stroke.
