Question

Why is the central region of intrafusal muscle fibres non-contractile?

a) Lack of myosin and actin filaments
b) Presence of myosin and actin filaments
c) Absence of sarcomeres
d) High concentration of mitochondria

Answer 1

The central region of intrafusal muscle fibers is non-contractile because it lacks actin and myosin filaments, which are organized into sarcomeres.

Step-by-step explanation:

The central region of intrafusal muscle fibers is non-contractile because it lacks the key components required for contraction, which are myosin and actin filaments, organized into sarcomeres. In the middle of these fibers, there are no sarcomeres or overlapping actin and myosin, which are essential for the muscle contraction process. Instead, the intrafusal muscle fibers serve a sensory function within muscle spindles, informing the central nervous system of muscle stretch.