Which statement best describes endolymph's role in vestibular transduction?

Which statement best describes endolymph's role in vestibular transduction?

• A. Hair cells are stimulated by gravity directly
• B. Endolymph is stationary during head movement
• C. Endolymph movement is required to stimulate hair cells
• D. Endolymph is outside the vestibular labyrinth

Answer: (C)

Endolymph movement provides the mechanical stimulus that deflects hair bundles and initiates vestibular transduction. Hair cells in the vestibular organs respond to bending of their stereocilia; this bending comes from the flow or relative movement of the endolymph inside the membranous labyrinth. When the head turns, the endolymph tends to lag due to inertia, causing it to flow within the semicircular canals and bend the hair cells via the cupula. In the otolith organs, gravity and linear acceleration cause the otolith-containing membrane to shift relative to the hair cells, with the surrounding endolymph helping transfer that force to deflect the stereocilia. This deflection opens mechanically gated potassium channels, depolarizing the hair cells and producing neural signals. That’s why endolymph movement is essential for transduction. Gravity doesn’t directly stimulate hair cells, but rather moves the otoliths in a way that ultimately requires endolymph-coupled deflection. Endolymph is not stationary during head movement, and it sits inside the vestibular labyrinth, not outside it.

Endolymph movement provides the mechanical stimulus that deflects hair bundles and initiates vestibular transduction. Hair cells in the vestibular organs respond to bending of their stereocilia; this bending comes from the flow or relative movement of the endolymph inside the membranous labyrinth. When the head turns, the endolymph tends to lag due to inertia, causing it to flow within the semicircular canals and bend the hair cells via the cupula. In the otolith organs, gravity and linear acceleration cause the otolith-containing membrane to shift relative to the hair cells, with the surrounding endolymph helping transfer that force to deflect the stereocilia. This deflection opens mechanically gated potassium channels, depolarizing the hair cells and producing neural signals.

That’s why endolymph movement is essential for transduction. Gravity doesn’t directly stimulate hair cells, but rather moves the otoliths in a way that ultimately requires endolymph-coupled deflection. Endolymph is not stationary during head movement, and it sits inside the vestibular labyrinth, not outside it.