Sarcoplasmic Reticulum

The sarcoplasmic reticulum (Figure 8.15) is a structure that surrounds each myofibril in muscle. The sarcoplasmic reticulum has a lumen within which it stores calcium ions. Upon stimulation by the nervous system, the sarcoplasmic reticulum depolarizes and releases calcium, which pours into the myofibrils and stimulates muscular contraction.

See also: The Structure of Muscle, The Sliding Filament Model, The Role of Calcium in Contraction, Transverse Tubules