Question

Contractile unit of muscle fibres is
A. Muscle fibre
B. Sarcomere
C. Myofibril
D. Sacrosome

Answer 1

Hint: A myocyte's cell membrane has many different areas, which may include the intercalated disks and the transverse tubular structure.

Complete Answer:
- Often known as a myocyte is a muscle cell and is the type of cell present in certain muscle tissue types. Myocytes grow out of myoblasts in a mechanism known as myogenesis to form muscles.
- There are two different myocyte types with distinct characteristics: cardiac, and smooth muscle cells.
- The skeletal muscles, on the other hand, are shaped by morphological units called muscle fibres. Skeletal muscle fibres help and pass the body and are called syncytia-multinucleated structures developed during embryonic development by combination of individual myoblasts.
- Smooth muscle cells regulate repetitive movements in the oesophagus and stomach, such as the contractions of peristalsis.

 Now, let us find the solution from the option.
- Broad, cylindrical chains of contractile proteins, or myofibrils, make up the entire cross section of the muscle fibre.
- One myofibril is composed of fragments called sarcomeres.
- There are muscle contractile modules.
- A dark stripe named a Z disc indicates the ends of a sarcomere and the beginnings of the next.

Thus, the correct option is (B) Sarcomere.

Note: Each muscle fibre includes myofibrils, the contractile units of the cell, which are very long chains of sarcomere. The myofibrils of smooth muscle cells do not contain sarcomeres.