where in the muscle cell is calcium stored
When muscles are at rest, calcium ions are stored in a cellular structure called the sarcoplasmic reticulum inside each muscle cell. In response to certain signals, the RYR1 channel releases calcium ions from the sarcoplasmic reticulum into the surrounding cell fluid (cytoplasm).hen muscles are at rest, calcium ions are stored in a cellular structure called the sarcoplasmic reticulum inside each muscle cell. In response to certain signals, the RYR1 channel releases calcium ions from the sarcoplasmic reticulum into the surrounding cell fluid (cytoplasm).