Osmosis video - Muscle spindles and golgi tendon organs

The muscle spindles and golgi tendon organs are proprioceptive sensory organs, which detect the change in muscle length, posture, and motion of body parts. The muscle spindles trigger the stretch reflex where an overstretched muscle spindle sends afferent signals through type Ia and type II sensory neurons to the spinal cord. Ia sensory neurons cause the contraction of the muscle and Ib causes the relaxation of the antagonist muscles.

The golgi tendon organs trigger the golgi tendon reflex when a muscle is being over-contracted. It then sends afferent signals through type Ib afferent fiber to the spinal cord, which triggers the inhibition of the contracting muscle and contraction of the antagonist muscles.