Question

Sarcomere is the functional unit of contraction in a muscle fiber. Identify the portion of myofibril that constitute a sarcomere.

• A. The portion of myofibril between two successive 'Z' line
• B. The portion of myofibril between two successive 'I' line
• C. The portion of myofibril between two successive 'A' line
• D. The portion of myofibril between two successive 'M' line

Answer 1

The correct option is A The portion of myofibril between two successive 'Z' line

• Sarcomere is a basic unit of the sarcomere. It is a portion of a myofibril between two successive 'Z' line.
• The I band is that part of the sarcomere that contains thin filaments, while the A band contains an area of overlap between the thin and the thick filaments.
• A single I band spans two neighboring sarcomeres. A Z line attaches those neighboring sarcomeres.
• The thin filaments are attached to the Z lines on each end of the sarcomere, while the thick filaments reside in the middle of the sarcomere.
  So, the correct answer is option A.