Muscle contraction essay question – Flashcards
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Nerve stimulus 1
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AP arrives at axon terminal and Ca2+ channels open, letting Ca2+ into the cell
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Nerve stimulus 2
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Ca2+ entry induces synaptic vessicles to release Ach into the synaptic cleft
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Nerve stimulus 3
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Ach crosses the synaptic cleft and binds to receptors on the sarcolemma, opening ion channels
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Nerve stimulus 4
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Na+ moves into the muscle fiber and K+ moves out for net depolarization
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Generation of AP across the sarcolemma 1
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The end plate potential spreads away in all direction from the neuromuscular junction
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Generation of AP across the sarcolemma 2
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The local depolarization triggers Na+ channels to open, letting Na+ flow into the cell, generating an action potential
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Generation of AP across the sarcolemma 3
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The AP moves down the cell causing more Na+ channels to open
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Generation of AP across the sarcolemma 4
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After the AP passes, Na+ channels close and K+ channels open letting K+ out and restoring electrical conditions, the Na+/K+ pumps then restore resting conditions
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EC coupling 1
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The action potential is transmitted along the t-tubule
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EC coupling 2
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AP changes the shape of voltage sensitive proteins in t-tubules causing SR channels to release Ca2+ into cytosol
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EC coupling 3
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Ca2+ binds to troponin and changes the shape of tropomyosin, exposing binding sites for myosin on the thin filaments
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EC coupling 4
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Myosin binds to actin forming cross bridges
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Cross bridge activity 1
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an energized myosin head attaches to an actin microfilament, forming a cross bridge
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Cross bridge activity 2
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ADP & P are released, the myosin head bends and pivots, sliding the actin filament towards the m line
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Cross bridge activity 3
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After ATP attaches to myosin, the myosin/actin link weakens and the myosin head detaches (cross bridge breaks)
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Cross bridge activity 4
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ATP is hydorlyzed to ADP and P, energy is released and the myosin head returns to its high energy cocked position
