The Golgi tendon organ lies at the junction between tendon and muscle. It consists of a group of collagen fibers (D14), which is surrounded by a thin sheath of connective tissue and is innervated by a myelinated nerve fiber (D15). The nerve fiber loses its myelin sheath after passing through the connective tissue capsule and divides into a number of branches that coil around the collagen fibers. The loosely arranged col-lagen fibers (E) are thought to tighten upon tension (F) and thus exert pressure onto the nerve endings. The resulting impulse is transmitted by the nerve fiber via the poste-rior root to the spinal cord. Here it has an in-hibitory effect on the motor neurons, thus preventing the muscle from excessive stretching or contraction.