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

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____The motor end plate generates an end-plate potential.          ​​​​

____The action potential spreads along the T-tubules, SR Ca2+ channels are pulled open, and Ca2+ flood the cytosol.          ​​​​

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

____Ca2+ 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.

Video transcript

Hey, everyone. Let's take a look at this question together. What is the role of calcium in muscle contraction? Is it? Answer choice. A calcium forces both acting and myosin to enter a relaxed state. Answer choice. B calcium triggers muscle contraction. Answer choice. C calcium remodels the muscle fibers or answer choice D all of the above. Let's work this problem out together to try to figure out which of the following answer choices best describes the role of calcium in muscle contraction. So in order to solve this question, we have to recall what we have learned about muscle contraction and the role that calcium plays in that muscle contraction, which we can recall that the calcium ions diffuse in the cytoplasm between the myosin and Acton filaments which that diffusion of the calcium ions in the cytoplasm between the myosin and act in filaments caused the filaments to shift. And when we say that the filaments are shifting, we are saying that the myo and act in filaments slide into each other which triggers muscle contraction. Therefore, the calcium ions which diffuse in the cytoplasm and cause the filaments to shift, triggers muscle contraction. So, answer choice B calcium triggers muscle contraction is the correct answer. And all other answer choices are incorrect since they do not correctly describe the role of calcium in muscle contraction. I hope you found this video to be helpful. Thank you and goodbye.