Golgi tendon organs are proprioceptive sense organs that are located at the insertion of skeletal muscle fibres into the tendons of skeletal muscle. The body of the organs are made up of strands of collagen that are connected at one end to the muscle fibres and at the other merge into the tendon proper. Each tendon organ is innervated by a single type Ib sensory afferent axon that branches and terminates as spiral endings around the collagen strands. During muscle contraction the strands of collagen are stretched as the muscle shortens. This stretching deforms the terminals of the Ib afferent axon, opening stretch-sensitive cation channels. As a result, the axon is depolarised and fires nerve impulses up to the central nervous system. The action potential frequency signals the force being developed within the muscle. This sensory feedback plays an important role in spinal reflexes and in the central control of muscle contraction. Specifically, it is postulated that because a golgi tendon organ exists in serial connection with muscle fibers, it can measure the tension that each muscle contraction builds up. When the anticipated tension exceeds the strength of the fiber, the golgi tendon organ signals an inhibition of muscle contraction, causing muscle collapse in an effort to prevent muscle damage from excessively heavy loads. Proprioception (from Latin proprius, meaning ones own) is the sense of the position of parts of the body, relative to other neighbouring parts of the body. ... A tendon or sinew is a tough band of fibrous connective tissue that connects muscle to bone. ... A top-down view of skeletal muscle Skeletal muscle is a type of striated muscle, attached to the skeleton. ... Collagen is the main protein of connective tissue. ... A cation is an ion with positive charge. ... A. Schematic of an electrophysiological recording of an action potential showing the various phases which occur as the wave passes a point on a cell membrane. ...