Which otolith organs detect linear acceleration and head tilt relative to gravity?

• A. Utricle and cochlea
• B. Utricle and saccule
• C. Saccule and cochlea
• D. Cochlea and semicircular canals

Answer: (B)

The key idea is that the otolith organs detect linear motion and gravity. The utricle and saccule are the otolith organs. Inside each is a macula with hair cells embedded in an otolithic membrane topped by otoconia crystals. When you move in a straight line or tilt your head, gravity and the inertia of the otoconia shift the membrane, bending the hair cells and signaling the motion to the brain. The utricle’s macula is oriented to sense horizontal linear acceleration and horizontal head tilt, while the saccule’s macula is oriented to sense vertical linear acceleration. Together they provide information about linear movement along all axes and gravity’s pull. The cochlea is for hearing, and the semicircular canals detect rotational (angular) acceleration, not linear acceleration.