MEDICAL PHYSIOLOGY

Detailed explanation-1: -Sarcomere is the contractile unit of a myofibril in striated muscle. The sarcomeres are joined end to end to form a myofibril. Each sarcomere is composed of a Z-line at either end, to which the actin filaments are attached. Thus, the correct answer is option (C), ‘Sarcomere’.

Detailed explanation-2: -The contraction unit is called sarcomere, which is the segment of the myofibril between two consecutive Z discs. This is about 4 µm in length in a relaxed muscle. During contraction, Z discs get as close as 1 µm. This happens because I bands are shortened when actin filaments are dragged over the myosin II filaments.

Detailed explanation-3: -The contractile functional unit of the myofibril is called the sarcomere, which is approximately 1.6–2.0 m in length.

Detailed explanation-4: -A sarcomere is the functional unit (contractile unit) of a muscle fiber. As illustrated in Figure 2-5, each sarcomere contains two types of myofilaments: thick filaments, composed primarily of the contractile protein myosin, and thin filaments, composed primarily of the contractile protein actin.

Detailed explanation-5: -A sarcomere is defined as the segment between two neighboring Z-discs and is composed of long, fibrous proteins such as myosin and actin [7].