What is the name of the calcium receptor found on the sarcoplasmic reticulum?

The ryanodine receptors are integral membrane proteins located on the sarcoplasmic reticulum (SR) of cardiac and skeletal muscle cells, and are critically involved in the process of calcium-induced calcium release.

When an action potential occurs in the muscle fiber, it leads to the opening of voltage-gated calcium channels on the cell membrane. This influx of calcium ions causes the ryanodine receptors on the sarcoplasmic reticulum to open, allowing stored calcium to be released into the cytoplasm. The increase in intracellular calcium concentration then facilitates contraction of the muscle fibers.

In contrast, calmodulin is a calcium-binding messenger protein that mediates various cellular processes but is not a receptor. Calcium ATPase is an enzyme responsible for pumping calcium ions back into the sarcoplasmic reticulum during muscle relaxation but does not serve as a receptor. Phospholamban is a regulatory protein that modulates the activity of the calcium ATPase in the sarcoplasmic reticulum but again is not a receptor for calcium.