Final answer:
Skeletal muscle fiber organization involves the sarcolemma, T-tubules, sarcoplasm, myofibrils composed of actin and myosin, and the sarcoplasmic reticulum that regulates calcium ions necessary for muscle contraction.
Step-by-step explanation:
Skeletal muscle fibers are specialized cells responsible for muscle contraction in the body. The cell membrane, known as the sarcolemma, encloses the fiber and is contiguous with the transverse (T) tubules which transmit nerve impulses into the cell. Within the cell is the sarcoplasm, akin to the cytoplasm of other cell types, which is rich in contractile elements called myofibrils. Myofibrils are themselves composed of repeated units called sarcomeres, the fundamental units of muscle contraction, which consist of actin (thin) and myosin (thick) filaments arranged in a striated pattern creating bands visible under a microscope.
Surrounding the myofibrils is the sarcoplasmic reticulum (SR), a specialized form of the endoplasmic reticulum that stores, releases, and retrieves calcium ions (Ca++), pivotal in triggering the contraction mechanism within muscle cells. During an action potential, the T-tubules communicate the signal to release Ca++ from the SR, thereby initiating the process of muscle fiber contraction.