ANATOMY

Detailed explanation-1: -The darker bands are called anisotropic bands (A bands). Together the I-bands and A-bands contribute to the striated appearance of skeletal muscle.

Detailed explanation-2: -The dark bands are called A bands and contain thick and thin filaments, with the thick filaments running the entire length of the A band.

Detailed explanation-3: -There are two types of myofilaments. Thin actin filament and thick myosin filament. Both the filaments are arranged alternately. The region where both myofilaments are present is seen as dark and is called as dark band.

Detailed explanation-4: -The dark A band consists of parallel myosin thick filaments, in a hexagonal arrangement in cross-section. The thick filaments of a single sarcomere are connected to each other by means of the M disc at their centres.

Detailed explanation-5: -Hint: The muscle fibres contain parallelly arranged myofibrils which have alternate light and dark bands. The dark present on the myofibril is called ‘A-band’ or anisotropic band and the light band present on the myofibril is called I-band or isotropic band.