Golgi tendon organ
The Golgi Tendon Organ is a sensory receptor that plays a key role in the reflex regulation of muscle contraction. They are particularly susceptible to muscle tension, whereas, muscle spindles are more sensitive to the passive stretching of motor fibres. In order to accurately detect muscle tension, they are in series with the extrafusal muscle fibres and are located at the junction between the tendon and motor unit.
The Golgi Tendon Organ is responsible for ensuring that no damage is inflicted upon muscle tendons. For this to occur a feedback loop must be maintained in order to prevent too high a tension building in the tendon. 1b axons are in constant contact with motor centres in the spinal cord. When tension gets too hight inhibitory signals are sent down 1b axons to a reflex arc in the spinal cord. Inhibitory signals are sent down the 1a afferent neurone controlling the motor unit, which reduces the force of contraction and relieving the tension in the tendon. This is a local circuit between the Golgi Tendon Organ and the Motor unit which runs off a negative feedback mechanism .