ec coupling.docx - Excitation-Contraction(EC coupling is...

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Excitation-Contraction (EC) coupling is the sequence of events by which transmission of an action potential along the sarcolemma causes myofilaments to slide 1. The Nerve Stimulus and Events at the Neuromuscular Junction a. When a nerve impulse reaches the end of an axon, the axon terminal releases ACh into the synaptic clef b. ACh diffuses across the clef and attaches to its receptors on the sarcolemma of the muscle fiber c. ACh binding triggers electrical events that ultimately generate an action potential 2. Generation of an Action Potential Across the Sarcolemma a. Generation of an end plate potential: binding of ACh molecules to its receptors at the neuromuscular junction opens chemically gated ion channels that allow both Na+ and K+ to pass. However, the driving force for Na+ is greater than that for K+ , more Na+ diffuses in than K+ diffuses out. A transient change in membrane potential occurs as the interior of the sarcolemma becomes less negative (depolarization).
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  • Spring '14
  • AnnD.Gathers

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