intrafusal muscle fibre

Intrafusal muscle fibers are specialized muscle fibers found within muscle spindles. These spindles are sensory receptors located in skeletal muscles that detect changes in muscle length and tension, providing crucial proprioceptive information to the central nervous system.123

Muscle spindles consist of a few intrafusal muscle fibers, which are thinner and shorter than regular skeletal muscle fibers. These intrafusal fibers have contractile ends and a non-contractile sensory midsection that is sensitive to stretch. When a muscle stretches, the intrafusal fibers are elongated, increasing nerve impulse frequency. This signals the central nervous system about the muscle's position and movement, contributing to coordinated muscle actions and reflexes like the knee-jerk reflex.12