The function of the terminal cisternae is to act as a calcium storage site. In muscle contraction, the calcium stored within the terminal cisternae is essential for proper function. This calcium storage site used for muscle contraction is not the same as the one utilized for bone tissue.
In the skeletal muscle, two terminal cisternae merge with a T tubule to form a triad structure. When a muscle is stimulated, calcium is released from the storage unit of the terminal cisternae. This calcium binds with troponin-C in the sarcoplasm to execute the muscle contraction.
Calcium's role as a muscle contraction activator was discovered during 20th century experiments on frog tissue.