The functional contractile unit of a myofibril is the
- A. myofilament
- B. sarcomere
- C. sarcolemma
- D. sarcoplasmic reticulum
Explanation
A sarcomere is the region between two Z lines, containing overlapping thick and thin filaments, and the whole muscle shortens because thousands of sarcomeres in series each shorten a little. A myofilament is a single actin or myosin strand, so it is a component rather than the unit. The sarcolemma is the cell membrane and the sarcoplasmic reticulum is the calcium store.
Related questions
During the contraction of a skeletal muscle, which of the following does NOT change in length?
According to the sliding filament theory, a muscle shortens because
Calcium ions start muscle contraction by binding to
Rigor mortis, the stiffening of muscles after death, occurs because
The neurotransmitter released at the neuromuscular junction of skeletal muscle is