Vestibulospinal tract axons arise from vestibular nuclei located in the pons and medulla. The medial vestibular nucleus gives rise to the medial vestibulospinal tract, which projects bilaterally to thoracic regions of the spinal cord, and the lateral vestibular nucleus gives rise to the lateral vestibulospinal tract, which descends ipsilaterally through the entire length of the spinal cord to synapse on interneurons in the anterior horn gray matter (eFig. 9.57). Given that the vestibular nuclei receive sensory input from the inner ear and cerebellum, this tract facilitates activity of extensor/antigravity muscles and inhibits activity of flexor muscles to maintain balance and an upright posture. As an example, the change in head position induced during tripping initiates extension of the upper limb and/or lower limb to prevent oneself from falling forward.