Question

Smooth muscle differs from striated muscle in many ways. Which of the following statements about the differences between smooth and striated muscle is NOT true?

a. The sarcoplasmic reticulum is much more extensive in smooth muscle than in striated muscle

b. Striated muscle cells organize their thick and thin filaments into sarcomeres, while smooth muscle cells scatter clusters of thick and thin filaments throughout the cytoplasm.

c. Striated muscle cells anchor thin filaments to Z disks, while smooth muscle cells anchor thin filaments to the cell membrane (via adhesion plaques) and to the cytoskeleton (via dense bodies).

d. Striated muscle has T-tubules while smooth muscle does not.

e. The ratio of thin filaments to thick filaments is greater in smooth muscle than in striated muscle.

Answer 1

a. The sarcoplasmic reticulum is much more extensive in smooth muscle than in striated muscle.

Sarcoplasmic reticulum is the structure found in muscle cell just similar to the endoplasmic reticulum in other cells.Their main function is to store calcium ions in muscle cells. During muscle contraction they release stored calcium ions and absorb calcium ions while muscle relaxation.

For the smooth muscle the sarcoplasmic reticulum is not well organised and they does not store Calcium ions, intead calcium ions comes from outside the cell. While in straited muscle the calcium ions stored in sarcoplasmic reticulum which helps in muscle contraction.