Which sensory organ detects linear acceleration and gravity?

• A. Semicircular canals
• B. Otolith organs
• C. Cochlea
• D. Visual cortex

Answer: (B)

The ability to sense linear acceleration and gravity comes from the otolith organs, the utricle and saccule, inside the vestibular system. These organs contain a gelatinous layer with tiny calcium carbonate crystals called otoconia. When the head tilts or experiences linear acceleration, inertia makes the otoconia lag, causing the layer to shift and deflect the embedded hair cells. This bending of the hair cells sends signals that tell you about your linear movement and your orientation relative to gravity.

The semicircular canals respond to angular (rotational) movements, not straight-line acceleration or gravity. The cochlea is involved in hearing, and the visual cortex processes visual information, not vestibular sensing. So, the organ that detects linear acceleration and gravity is the otolith organs.