A) cardiac fibres
B) non-striated fibres
C) myofibril of striated muscle
D) All of the above
Correct Answer: C
Solution :
Each striated muscle, consists of numerous muscle fibres segregated into several small parallel bundles called fasciculi. The dark bands of the myofibril are termed A-band (Anisotropic band). Each A-band has as a middle light zone called H-zone (Hensons line). The light bands are also called I-band (Isotropic band). The sarcolemma is invaginated to form T-tubules (Transverse tubules). The T-tubules form a simple mechanism of transportation of nutrients and carry signals for the contraction of myofibrils from the sarcolemma to the interior. The part of the myofibril between two successive Z-lines is called sarcomere. Therefore, the sarcomere comprises A-band and half of each adjacent I-band. A sarcomere is about 2 to 3 (im long. The sarcomere is the functional unit of contractile system in muscle. In fact, each sarcomere is a bundle of primary and secondary filaments.
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