Calcium channel that mediates the release of Ca2+ from the sarcoplasmic reticulum into the cytoplasm in muscle and thereby plays a role in triggering muscle contraction. May regulate Ca2+ release by other calcium channels. Calcium channel that mediates Ca2+-induced Ca2+ release from the endoplasmic reticulum in non-muscle cells. Contributes to cellular calcium ion homeostasis (By similarity). Plays a role in cellular calcium signaling.