Anatomy & Physiology part 1

The anatomy and physiology of the vestibular system are presented as the foundation for accurate assessment, interpretation of findings, and effective rehabilitation. Learners are shown how visual, proprioceptive, and vestibular inputs are integrated in the brainstem, and why proprioception is most important for balance, while sudden dizziness more often points to vestibular dysfunction. The explanation then focuses on the inner ear balance organs: the three semicircular canals, utricle, and saccule. It covers what each structure detects, how the vestibular nerve divides into superior and inferior branches, and why this matters clinically in conditions such as vestibular neuritis. Head positioning for testing is linked directly to canal anatomy, including the 30-degree orientation of the lateral canals and the paired planes of the vertical canals. Further sections explain fluid movement, hair cell deflection, otoconia, gravity, and signal excitation versus inhibition. Clinical relevance is highlighted through examples including Menière’s disease, labyrinthitis, vascular lesions, motion perception errors during acceleration, and compensation mechanisms such as sensory reweighting, desensitization, and central adaptation after unilateral vestibular loss.