Coordination and response CIE A Level Biology revision
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Explain the events in the presynaptic neuron at the neuromuscular junction starting with the arrival of an action potential
diffusion of Ca2+ into neuron causes movement of vesicles containing acetylcholine which diffuses across the synapse to fuse with the presynaptic membrane
What happens after acetylcholine diffuses into the synaptic cleft?
it binds with receptors on the sarcolemma causing Na+ channels to open and Na+ to diffuse in and depolarise the membrane and initiate an action potential
What happens in the muscle fibers after the action potential is initiated?
depolarisation spreads down the T-tubules, channel proteins for Ca2+ open and Ca2+ ions diffuse out of the SR, bind to troponin
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