Excitation-contraction coupling is the process that links the electrical excitation of a muscle cell to the mechanical contraction of its myofilaments. The sequence of events is as follows:

1. An action potential travels along the muscle cell's sarcolemma.

2. The action potential causes the release of calcium ions from the sarcoplasmic reticulum (SR), the muscle cell's internal calcium store.

3. The calcium ions bind to troponin, a protein complex on the thin filaments of the myofilaments.

4. The binding of calcium to troponin causes a conformational change in the troponin-tropomyosin complex that allows the myosin heads to bind to the actin filaments.

5. The myosin heads then undergo a power stroke, pulling the thin filaments toward the center of the sarcomere and causing muscle contraction.

6. The contraction ends when the action potential ends and the calcium ions are pumped back into the SR.

The process of excitation-contraction coupling is essential for muscle contraction. Without it, muscles would not be able to function.