Q.The functional unit of a muscle fibre is
a. sarcomere
b. sarcoplasm
c. myosin
d. actin

Skeletal (voluntary) muscle is anchored to bone by a tendon and is organised as a nested hierarchy of connective-tissue-wrapped bundles: the whole muscle (wrapped in epimysium) is divided into fascicles (wrapped in perimysium), each fascicle made of individual muscle fibres (wrapped in endomysium).

Each muscle fibre is a single elongated, multinucleate cell whose plasma membrane is the sarcolemma and whose cytoplasm is the sarcoplasm, rich in glycosomes (stored glycogen), myoglobin (an oxygen-storing red pigment) and an extensive sarcoplasmic reticulum (which stores calcium). Hundreds to thousands of parallel myofibrils run the fibre's length, each showing a repeating pattern of dark A-bands and light I-bands that gives the whole fibre its striated appearance — the alternating bands are perfectly aligned across adjacent myofibrils, which is what makes the striping vi …