What structure of skeletal muscle functions stores calcium?

The structure of skeletal muscle that functions to store calcium is called the sarcoplasmic reticulum (SR). The SR is a network of membrane-bound sacs located within the muscle fiber. It serves as a calcium reservoir, releasing calcium ions into the cytoplasm when the muscle is stimulated to contract. The release of calcium from the SR is triggered by the action potential, which causes a conformational change in the ryanodine receptors (RyRs) on the SR membrane, allowing calcium ions to flow down their concentration gradient into the cytoplasm. The SR also plays a role in muscle relaxation by reabsorbing calcium ions back into the SR.