Assertion`:-` When the muscle fibre contracts, sacromere length is reduced.
Reason `:-` Sliding of myosin filament occurs due to rotational movement of myosin head.

Assertion : During muscle contraction I-band and A-band get reduced. Reason :- During contraction thin filament slides over myosin filament.

Assertion :- In the contraction of muscle myosin slide on actin filament. Reason : Actin become constant & myosin shows rotational movement proved by sliding filament theory :

Assertion : - Ca^(++) play an important role in the muscle contraction. Reason :- Calcium bind with a subunit of troponin on actin filaments and thereby remove the masking of active sites for myosin.

Assertion : In muscle contraction, length of both A-bands and I-bands decrease. Reason : Both myosin of A-band and actin of I-bands are contractile proteins and decrease in size during muscle contraction.

Assertion : Contraction of a muscle fibre takes place by the sliding of the thin filaments over the thick filaments. Reason : The central part of thick filament is not overlapped by thin filaments in a resting state.

Assertion : Contraction of a muscle fibre takes place by the sliding of the thin filaments over the thick filaments. Reason : The central part of thick filament is not overlapped by thin filaments in a resting state.

During contraction of a muscle fibre, the length of sarcomere decreases due to decrease in length of

Assertion: Mechanism of muscle contraction is expalained by sliding-filaments theory. Reason: Contraction of muscle fibre takes place by the sliding of thick filaments over the thin filaments.

Assertion: Mechanism of muscle contraction is expalained by sliding-filaments theory. Reason: Contraction of muscle fibre takes place by the sliding of thick filaments over the thin filaments.