Anatomy & Physiology part 2

Vestibular processing in the brainstem, vestibular nuclei, and cerebellum is presented as the basis for gaze stability, upright head position, and postural alignment. The main goal is to keep visual targets centered on the fovea so vision stays clear during head and body movement. Three gaze-control mechanisms are outlined: the vestibulo-ocular reflex, the cervical-ocular reflex, and optokinetic reflexes. Particular emphasis is placed on the vestibulo-ocular reflex, which produces compensatory eye movements opposite to head movement, and on the limited importance of the cervical-ocular reflex in healthy individuals. The explanation also covers central eye movement systems, including saccades, smooth pursuit, and optokinetic responses. Learners are guided through the neural pathways linking the semicircular canals to the eye muscles, especially the lateral canal pathways involving the vestibular nuclei, abducens nucleus, and medial longitudinal fasciculus. Clinical relevance is highlighted through internuclear ophthalmoplegia as an early sign of multiple sclerosis, along with abnormal smooth pursuit and delayed adduction. The summary also connects vestibular output to vomiting, spatial perception, cerebellar balance control, and vestibulospinal effects on limb and trunk posture.