Which structure detects angular velocity about its axis, contributing to 3D rotation sensing?

• A. Semicircular canals detect angular velocity about their axes.
• B. Otolith organs detect angular velocity.
• C. Cochlea detects angular velocity.
• D. Vestibular nerve detects angular velocity directly.

Answer: (B)

Angular velocity about the head’s axes is detected by the semicircular canals. Each canal has hair cells in a cupula that respond when endolymph moves as the head rotates; this bending of hair cells encodes rotational speed. With three canals oriented in different planes, the brain combines their signals to sense rotation in 3D. By contrast, the otolith organs (utricle and saccule) detect linear acceleration and head tilt relative to gravity, not rotation. The cochlea handles hearing, and the vestibular nerve is the pathway for these signals, not the detector itself.