Excitation contraction coupling Results in calcium ion release from SR

Excitation contraction coupling results in calcium

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Excitation-contraction coupling Results in calcium ion release from SR Neuromuscular junction 1 junction / muscle fiber Axon terminal Synaptic vesicles contain neurotransmitter A c e ty lc h o lin e ( A c h ) Motor end plate S a r c o le m m a s e c tio n w ith r e c e p to r s f o r A c h Ach receptors: C h e m ic a lly - g a te d N a c h a n n e ls Acetylcholinesterase (AchE)
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5/21/19 6 Skeletal muscle innervation Skeletal muscle innervation Resting NM J Ach vesicles sit in axon Skeletal muscle innervation Signal (action potential) arrives at NM J
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5/21/19 7 Skeletal muscle innervation Vesicles fuse with neuron membrane Ach released into synapse Skeletal muscle innervation Ach binds to receptors (chemically gated Na + channels) Channel opens Na + ions diffuses in Skeletal muscle innervation Na + movement generates action potential on sarcolemma Acetylcholinesterase (AchE) breaks down Ach
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5/21/19 8 Action potential (excitation) spreads along the – sarcolemma – down the T-tubules – releases Ca + 2 ions from the SR Recall myofibril arrangement Exposure of active sites results in cross-bridge formation
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5/21/19 9 Contraction cycle cycling of myosin heads… Calcium ions released
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