Which fluid moves during head movement to deflect vestibular hair cells?

Which fluid moves during head movement to deflect vestibular hair cells?

• A. Endolymph
• B. Perilymph
• C. CSF
• D. Interstitial fluid

Answer: (A)

Endolymph movement inside the semicircular canals deflects vestibular hair cells. When you rotate your head, the endolymph lags due to inertia, creating flow that pushes on the cupula in the ampulla. This bending of the hair cell stereocilia opens mechanotransduction channels and sends a signal to the brain about angular motion. Perilymph surrounds the membranous labyrinth but doesn’t drive the cupula’s deflection, and CSF or interstitial fluid don’t participate in this mechanism. This is how the system detects angular acceleration rather than linear movement.

Endolymph movement inside the semicircular canals deflects vestibular hair cells. When you rotate your head, the endolymph lags due to inertia, creating flow that pushes on the cupula in the ampulla. This bending of the hair cell stereocilia opens mechanotransduction channels and sends a signal to the brain about angular motion. Perilymph surrounds the membranous labyrinth but doesn’t drive the cupula’s deflection, and CSF or interstitial fluid don’t participate in this mechanism. This is how the system detects angular acceleration rather than linear movement.