Which statement best describes the semicircular canal?

• A. A sensor that measures static pressure in the ear canal.
• B. An inner ear organ that detects angular acceleration of the body.
• C. A type of radar altimeter used for measuring altitude.
• D. A flight control surface on the vertical tail.

Answer: (B)

The semicircular canals are part of the inner ear’s balance system and specialize in detecting rotational, or angular, movement. They contain hair cells in a swollen area called the ampulla, with fluid (endolymph) inside each canal. When you rotate your head, the fluid lags behind because of inertia, bending those hair cells and converting the motion into neural signals that indicate angular velocity. Because the response depends on a change in rotation, these canals are most sensitive to angular acceleration, and they help your brain sense head motion and stabilize your gaze through the vestibulo-ocular reflex. There are three canals arranged in perpendicular planes, so they can sense rotation about any axis.

They don’t measure static pressure in the ear canal, they aren’t a radar altimeter, and they aren’t a flight control surface. Static pressure sensing or altitude measurement isn’t the function of the vestibular system; a pedestal or instrument on the aircraft handles those tasks, while a flight control surface is a physical part of the aircraft, not a sensory organ.