Lihasspindelin

Lihasspindelin, also known as muscle spindle, is a sensory receptor found in skeletal muscles. It plays a crucial role in proprioception, the sense of the relative position of one's own parts of the body and strength of effort being employed in movement. Muscle spindles are embedded within the muscle fibers and are composed of a few specialized muscle fibers called intrafusal fibers, surrounded by a connective tissue capsule.

These sensory receptors are innervated by both afferent and efferent nerve fibers. The afferent fibers transmit sensory information about muscle length and the rate of change in muscle length to the central nervous system. The efferent fibers, originating from motor neurons, innervate the intrafusal fibers, allowing for adjustments in spindle sensitivity.

The primary function of muscle spindles is to detect and report changes in muscle length. When a muscle stretches, the muscle spindle is activated, sending signals to the spinal cord. This signal can trigger a reflex arc, leading to a contraction of the same muscle to resist the stretch, a phenomenon known as the stretch reflex. This reflex is vital for maintaining posture, balance, and smooth, coordinated movements. They also contribute to the sense of limb position and movement, allowing us to be aware of where our body parts are in space without looking.