The arrangement of vestibular organs makes them most sensitive to which stimulus?

• A. Changes in acceleration
• B. Gravity
• C. Sound frequency
• D. Temperature

Answer: (A)

The vestibular system is built to sense how the head moves through space by detecting accelerations. The otolith organs (utricle and saccule) have hair cells embedded in a gel with calcium carbonate crystals that respond when linear speed or head tilt causes inertia to lag the motion, bending the hair cells and signaling linear acceleration along different axes. The three semicircular canals are oriented in orthogonal planes and detect angular acceleration through the movement of endolymph fluid inside each canal, bending hair cells to register rotational changes. Because gravity is a constant influence, the most informative and robust signals come from changes in acceleration rather than a steady gravitational pull. Sound frequency and temperature are not primary cues processed by the vestibular sensors in this context, which is why the arrangement best supports detecting changes in acceleration.