Answer: Sarcoplasmic reticulum.
- A Golgi apparatus
- B Cell nucleus
- C Mitochondrial matrix
- D Sarcoplasmic reticulum
Correct answer: D. Sarcoplasmic reticulum
Explanation: The sarcoplasmic reticulum stores Ca<sup>2+</sup> and releases it on stimulation to trigger 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.