Question

Body balance during dynamic condition is initiated by which structure?

• A. Otoconia
• B. Cupula
• C. Stereocilia of crista
• D. Kinocilium of maculae

Answer 1

The correct option is B Cupula

The cupula is a structure in the vestibular system, providing the sense of spatial orientation. The cupula is located within the ampullae of each of the three semicircular canals. Part of the crista ampullaris, the cupula has embedded hair cells that have several stereocilia associated with each kinocilium. The cupula itself is the gelatinous component of the crista ampullaris that extends from the crista to the roof of the ampullae. When the head rotates, the endolymph filling the semicircular ducts initially lags behind due to inertia. As a result, the cupula is deflected opposite the direction of head movement. As the endolymph pushes the cupula, the stereocilia are bent as well, stimulating the hair cells within the crista ampullaris. After a short time of continual rotation, however, the endolymphs acceleration normalizes with the rate of rotation of the semicircular ducts. As a result, the cupula returns to its resting position and the hair cells cease to be stimulated. This continues until the head stops rotating which simultaneously halts semicircular duct rotation.