Question

In a myofibril , the peripheral part of A band is
A) With actin filaments only
B) With myosin filaments only
C) Both actin and myosin filaments
D) Without filaments.

Answer 1

Hint: Myofibrils are also called muscle fibers which are basically rod shaped structures. They are composed of myocytes which are known as muscle fibers.

Complete answer:
A myofibril also well-known as a muscle fibril is a basic rod-like unit of a muscle cell. Muscles are composed of tubular cells called myocytes,which is known as muscle fibres in striated muscle, and these cells in turn are composed of many chains of myofibrils. They are formed during embryonic development in a process which is known as myogenesis.

Myofibrils are composed of a long proteins as well as the following such as actin, myosin, and titin, and other proteins that clutch them jointly. These proteins are pre arranged into thick and thin filaments called myofilaments, which replicate along the length of the myofibril in sections called sarcomeres. Muscles contract by sliding the thick myosin and thin actin filaments down each other. A group of myofibrils are generally called sarcomere.

They are very fine contractile fibres, groups of which expand in parallel columns along the length of striated muscle fibres. The myofibrils are prepared with thick and thin myofilaments, which help to give the muscle its striated manifestation. Muscular contraction is caused by the communication between actin and myosin as they temporarily attach to each other and are released.

The myofibrils contain thick and thin filaments. The arrangement of thick myosin filaments along the myofibrils and the cell cause them to refract light and produce a dark band which is known as an A band. The anisotropic band is composed of both thick and thin filaments.

Therefore the correct answer is option (C) both actin and myosin filaments.

Note:Myofibrils are the functional unit of skeletal muscles. Their main function is to perform muscle contraction. The sacromers which are present in them are responsible for the muscle contraction.