Q.Write true or false. If false change the statement so that it is true.

1. True. Actin is present in the thin filament.
2. False. The H-zone represents only the thick filaments — it is the central part of the thick filaments that the thin filaments do not overlap. Corrected: "H-zone of striated muscle fibre represents only the thick filaments (the part not overlapped by thin filaments)."
3. True. The human skeleton has 206 bones.
4. False. There are 12 pairs of ribs in man. Corrected: "There are 12 pairs of ribs in man." …

Each statement is judged against the structure of muscle and the make-up of the human skeleton, and where a statement is false it is rewritten to be correct.

1. Actin is present in thin filament. — True. The thin filament is built from actin, which is why it is thinner than the myosin-containing thick filament. Actin lies in the light I-band and is anchored to the Z-lines.
2. H-zone of striated muscle fibre represents both thick and thin filaments. — False. The H-zone is the central portion of the A-band where only the thick filaments are present, that is, the part of the thick filaments that the thin filaments do not reach or overlap. It therefore represents thick filaments alone, not both.

   Corrected statement: The H-zone of a striated muscle fibre represents only the thick (myosin) filaments — the central part not overlapped by the thin filaments.

3. Human skeleton has 206 bones. — True. The adult human skeletal system is made up of 206 bones together with a few cartilages, organised into the axial and appendicular divisions.
4. There are 11 pairs of ribs in man. — False. There are 12 pairs of ribs — 7 pairs of true ribs, 3 pairs of false ribs, and 2 pairs of floating ribs. …