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NEET Biology · Human Physiology

Locomotion and movement

Taught in NCERT Class 11 Biology, Chapter 17: Locomotion and Movement.

3 verified questions: Easy 1 · Medium 2 · NEET level 0

Sample questions

Sample 1Easy

The portion of a myofibril between two successive Z lines, considered the functional unit of contraction, is the

  1. A

    sarcomere

  2. B

    sarcoplasm

  3. C

    sarcolemma

  4. D

    fascicle

Show the answer
The answer is A.

The part of the myofibril between two successive Z lines is the sarcomere, the functional unit of contraction. During contraction the Z lines are pulled closer and the sarcomere shortens.

  • B.

    Sarcoplasm is the cytoplasm of the muscle fibre.

  • C.

    Sarcolemma is the plasma membrane lining the muscle fibre.

  • D.

    A fascicle is a bundle of muscle fibres held together by connective tissue.

NCERT: Class 11 Biology, Chapter 17 (Locomotion and Movement), Structure of Contractile Proteins

Sample 2Medium

A figure shows one sarcomere of a myofibril. P is a light band, bisected by a dark line S. Q is a dark band in the middle of the sarcomere, and R is a less dense zone at the centre of Q. The sarcomere lies between two S lines. When the muscle contracts, which labelled band keeps its length?

  1. A

    P, the I band

  2. B

    Q, the A band

  3. C

    R, the H zone

  4. D

    The distance between two S lines

Show the answer
The answer is B.

In the sliding filament theory, the thin filaments slide towards the centre over the thick filaments. The Z lines come closer and the I bands shorten, but the A bands, which match the length of the thick filaments, keep their length.

  • A.

    The I band (P) gets shorter during contraction, as the thin filaments slide over the thick filaments.

  • C.

    The H zone (R) narrows during contraction, as the thin filaments slide in from both sides.

  • D.

    S is the Z line. The Z lines are pulled closer together during contraction, so the sarcomere shortens.

NCERT: Class 11 Biology, Chapter 17

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