Question

select the correct answer. a skeletal muscle is a composition of several components bundled one into the other. at which structural level in the muscle does contraction occur to bring about contraction in the whole muscle? a. myofibril b. muscle fiber c. myoneural junction d. tendon e. fascicle

Explanation:

To solve this, we analyze each option:

• Option A: Myofibrils contain sarcomeres, the functional units for contraction, but contraction at the myofibril level contributes to muscle fiber contraction.
• Option B: A muscle fiber (a single muscle cell) contains myofibrils. Contraction occurs within the muscle fiber (due to myofibril/sarcomere activity) and this contraction of individual muscle fibers leads to the whole muscle contracting.
• Option C: Myoneural junction is the connection between a nerve and muscle, involved in triggering contraction, not the site of contraction itself.
• Option D: Tendon connects muscle to bone, transmitting force, not contracting.
• Option E: Fascicle is a bundle of muscle fibers, contraction of muscle fibers (within fascicles) causes fascicle and whole muscle movement, but the contraction originates at the muscle fiber (cell) level with its myofibrils.

The muscle fiber (muscle cell) is the structural level where the contraction machinery (myofibrils with sarcomeres) is organized, and the contraction of muscle fibers leads to whole - muscle contraction.

Answer:

B. muscle fiber