Concept:Chronological sequence of Excitation-Contraction Coupling.
Formula:N/A (Conceptual)
Solution:- Step 3: The action potential from the motor neuron first arrives at the neuromuscular junction, releasing acetylcholine.
- Step 1: This depolarizes the muscle cell, sending the electrical wave sweeping across the sarcolemma and diving deep into the cell via the T-tubules.
- Step 2: The deep T-tubules physically contact the terminal cisternae of the sarcoplasmic reticulum, passing the shockwave to it.
- Step 4: This final shock forces the voltage-gated Ca\(^{2+}\) channels in the SR to blast open, flooding the cell with calcium to trigger contraction.
Why other options are incorrect:Any other sequence breaks the laws of physical causality. The signal must hit the outside of the cell (junction) before it can dive inside (T-tubules) to unlock the internal calcium vault (SR).
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