A receptor organ (see proprioceptor) located at the junction between a skeletal muscle and its tendon that detects contraction of the muscle. Named after Camillo Golgi, it consists of an encapsulated bundle of collagen fibres that penetrate the muscle at one end and the tendon at the other. The organ is supplied by an afferent neuron, whose sensory endings (dendrites) wrap around the collagen fibres. Contraction of the muscle causes stretching of the collagen fibres, which stimulates the sensory neuron. This relays signals via interneurons in the central nervous system, causing the inhibition of motor neurons supplying the same muscle and hence its relaxation. These signals also lead to the excitation of antagonistic (opposing) muscles. This inverse myotatic response protects muscles from tearing or detachment due to excessive contraction forces.