ANATOMY

Detailed explanation-1: -The specialized smooth endoplasmic reticulum, called the sarcoplasmic reticulum (SR), stores, releases, and retrieves calcium ions (Ca++).

Detailed explanation-2: -Similar to the endoplasmic reticulum of other cells, sarcoplasmic reticulum surrounds each myofibril and stores calcium ions. The sarcoplasmic reticulum (SR) is a membrane-bound structure within muscle cells that functions primarily in the storage of calcium ions (Ca2+).

Detailed explanation-3: -Myofibril Structure Each myofibril is surrounded by the sarcoplasmic reticulum, which is closely associated with the transverse tubules.

Detailed explanation-4: -When the muscle is stimulated, calcium ions are released from its store inside the sarcoplasmic reticulum, into the sarcoplasm (muscle ).

Detailed explanation-5: -Calcium ions at rest are stored in the sarcoplasmic reticulum (SR) from which they are rapidly released upon the depolarisation of the sarcolemmal and transverse (T-) tubular membranes of the muscle cell.