The fluid-filled chamber in the inner ear that detects changes in gravity is called the utricle.

Here's why:

* Utricle and Saccule: The utricle and saccule are two fluid-filled sacs within the inner ear's vestibular system, responsible for detecting linear acceleration and gravity.

* Gravity Detection: The utricle specifically contains sensory hair cells that are embedded in a gelatinous structure called the otolithic membrane. This membrane contains tiny calcium carbonate crystals called otoconia, which are heavier than the surrounding fluid. When the head tilts, the otoconia shift due to gravity, bending the hair cells and sending signals to the brain about the head's position.

So, while both the utricle and saccule are involved in balance, it is the utricle that plays the primary role in detecting changes in gravity.