Answer: Sarcomere.
- A Myofibril
- B Sarcomere
- C Muscle fibre
- D Actin filament
Correct answer: B. Sarcomere
Explanation: The sarcomere is the functional unit of muscle contraction. It extends from Z disc to Z disc and contains interdigitating thick (myosin) and thin (actin) filaments that slide past each other during contraction.
A sarcomere (Z line to Z line): during contraction the I band and H zone shorten as thin filaments slide over thick, while the A band stays the same length. Image: SlothMcCarty, CC BY-SA 3.0, via Wikimedia Commons.
Concept context
Types of movement, muscle contraction, skeletal system, joints, and disorders. Important for Class 11 and NEET.