The semicircular canals detect angular acceleration around which axis?

• A. They detect linear acceleration only
• B. They detect gravity only
• C. They detect angular acceleration around each axis
• D. They detect sound frequency

Answer: (C)

Rotational motion sensing in the vestibular system is handled by the semicircular canals, of which there are three oriented along three perpendicular axes. When you start or change a turn, your head’s angular velocity changes. The endolymph inside a canal lags behind this motion, deflecting the cupula and bending the hair cells in the ampulla. This triggers neural signals that correspond to the rate of change of angular velocity—angular acceleration. Once rotation becomes steady, the endolymph catches up and the deflection dies away, so signals taper off. Because the three canals align with the three axes, angular acceleration is detected about each axis. Gravity and linear acceleration are detected by the otolith organs, and sound by the cochlea, not the semicircular canals.