Which statement about otolith organs is true?

• A. They detect angular acceleration
• B. They detect gravity only
• C. They are part of the semicircular canals
• D. They detect linear acceleration and gravity

Answer: (D)

Otolith organs detect linear acceleration and gravity. They’re the utricle and saccule inside the vestibule, containing otoliths (small crystals) that add inertia to the hair cell layer. When you tilt your head or experience forward or sideways acceleration, gravity and the inertial response of the otoliths cause a deflection of the hair cell cilia. This changes the rate of nerve impulses sent to the brain, providing information about static head orientation relative to gravity and about linear, straight-line motion.

Angular (rotational) acceleration, such as turning or spinning, is detected by the semicircular canals, which respond to fluid movement and cupula deflection in their ampullae. The otolith organs are not part of the semicircular canals; they are separate structures that specifically convey linear acceleration and gravity cues.

So the statement that otolith organs detect linear acceleration and gravity is correct.