Intrafusal fibers are embedded within which structure?

Intrafusal fibers are embedded within which structure?

• A. Muscle spindle
• B. Tendon
• C. Perimysium
• D. Endomysium

Answer: (A)

Intrafusal fibers are specialized components of a muscle spindle, the sensory receptor that detects stretch. They are embedded inside the muscle spindle, which sits in parallel with the ordinary contractile (extrafusal) fibers. The spindle is enclosed by a capsule and connective tissue, and the intrafusal fibers within it remain distinct from the surrounding extrafusal fibers. This arrangement lets the muscle spindle monitor changes in length and the rate of that change, contributing to proprioception and the stretch reflex. The tendon contains the Golgi tendon organ, not intrafusal fibers, and the perimysium and endomysium wrap fascicles and individual fibers outside of the spindle structure, respectively.

Intrafusal fibers are specialized components of a muscle spindle, the sensory receptor that detects stretch. They are embedded inside the muscle spindle, which sits in parallel with the ordinary contractile (extrafusal) fibers. The spindle is enclosed by a capsule and connective tissue, and the intrafusal fibers within it remain distinct from the surrounding extrafusal fibers. This arrangement lets the muscle spindle monitor changes in length and the rate of that change, contributing to proprioception and the stretch reflex. The tendon contains the Golgi tendon organ, not intrafusal fibers, and the perimysium and endomysium wrap fascicles and individual fibers outside of the spindle structure, respectively.