The action potential on the muscle cell leads to contraction due to the release of calcium ions. where are calcium ions stored in the muscle cell?

Sarcoplasmic reticulum.

Explanation:

The muscle cells are the excitable cells that has the ability to generate the action potential. The muscle cells helps in the contraction and controls the body movement.

The calcium ions plays an important role in the action potential of the muscle cell. The calcium ions are stored in the terminal cisterns of the sarcoplasmic reticulum. The sarcoplasmic reticulum acts as the main storage site for the calcium ions.

Thus, the answer is sarcoplasmic reticulum.

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