A sensory organ in the tendon that recognizes changes in tension in the muscle.
A spindle-shaped structure at the junction of a muscle and a tendon. This structure is thought to function as a feedback system that senses muscle tension through tendon stretch, inhibits muscle contraction of the agonist, and facilitates contraction of the antagonistic muscle. The purpose of this mechanism, known as autogenic facilitation, is to prevent overuse and damage to the muscle and corresponding joint.