Final answer:
The sarcoplasm is the cytoplasm of a muscle cell, surrounded by the sarcolemma. The sarcoplasmic reticulum is a specialized smooth endoplasmic reticulum that stores calcium ions.
Step-by-step explanation:
The sarcoplasm is the cytoplasm of a muscle cell, located inside the sarcolemma (plasma membrane) and surrounding the myofibrils. It contains important components for muscle contraction, such as mitochondria for energy production and the sarcoplasmic reticulum for calcium storage.
The sarcolemma is the cell membrane of a muscle fiber. It encloses the sarcoplasm and regulates the movement of substances in and out of the cell.
The sarcoplasmic reticulum (SR) is a specialized smooth endoplasmic reticulum within the sarcoplasm. It stores, releases, and retrieves calcium ions (Ca++), which play a crucial role in muscle contraction.