ABSTRACT
In the ampullae, the hair cells are lined, at intervals, along the ampullary crest, which runs at right angles to the direction of the canal. The hair cells along this ridge have stereocilia and a longer kinocilium, encased in a gelatinous cupula that extends to the roof of the ampulla and acts like a sail. Movement of the head creates a fluid inertia that displaces the cilia. Movement in one direction depolarizes the hair cell, causing transmitter release and increasing the firing rate of the vestibular primary afferent neurons. Movement in the opposite direction causes hyperpolarization. It is worth noting that movement that causes depolarization of primary afferents in one labyrinth will have the opposite effect in the labyrinth of the contralateral ear.
