When describing the muscle excitation-coupling sequence, all of the following are
true EXCEPT
1. An action potential arrives at the neuromuscular junction and
triggers the release of the neurotransmitter, acetylcholine
2. Ca 2+ binds to troponin causing it to change shape, exposing binding
sites for myosin on the actin filaments
3. ADP binds onto actin allowing it to release the myosin heads ready
for the next action potential to arrive
4. The postsynaptic action potential propagates along the sarcolemma
and down the T-tubules