Chapter 10, Problem 8CYR

Order the following events of excitation and excitation-contraction coupling. Put 1 by the first event, 2 by the second, and so on.

_______The motor end plate generates an end-plate potential.

________ The action potential spreads along the T-tubules, SR ${\text{Ca}}^{2+}$ channels are pulled open, and ${\text{Ca}}^{2+}$ flood the cytosol.

________Acetylcholine binds to receptors on the motor end plate, and ligand-gated ion channels open.

_______ ${\text{Ca}}^{2+}$ bind troponin, which allows tropomyosin to move away from the actin active site, initiating a contraction cycle.

______The action potential propagates through the sarcolemma and dives deeply into the cell along the T-tubules.