NEETZoologyLocomotion and Movement
Match List-I with List-II regarding the events of muscle contraction. List-I List-II A. Maximally contracted muscle I. Calcium ions are pumped back to sarcoplasmic cisternae B. Resting state of muscle II. H-zone disappears completely C. Initiation of contraction III. Masking of active sites for myosin on actin filaments D. Muscle relaxation IV. Calcium binds to a subunit of troponin Choose the correct answer from the
Options
- AA-II, B-IV, C-III, D-I
- BA-III, B-II, C-IV, D-I
- CA-II, B-III, C-I, D-IV
- DA-II, B-III, C-IV, D-I
Correct answer
D. A-II, B-III, C-IV, D-I
Step-by-step solution
During maximal contraction of the muscle, the actin filaments are pulled deeply into the A-band, causing the H-zone to disappear completely (A matches II). In a resting state of the muscle, a subunit of troponin masks the active binding sites for myosin on the actin filaments (B matches III). Contraction is initiated when calcium ions bind to a subunit of troponin on actin filaments, which removes the masking of active sites for myosin (C matches IV). Muscle relaxation occurs when calcium ions are pumped back to th