Fluid-filled structures within the inner ear that provide information about dynamic equilibrium.

Fluid-filled structures within the inner ear that provide information about dynamic equilibrium.

• A. Vestibule
• B. Cochlea
• C. Semicircular canals
• D. Oval window

Answer: (C)

Dynamic equilibrium is sensed by the semicircular canals, a set of fluid-filled channels in the inner ear. Each canal is oriented in a different plane, so they detect rotation around different axes. Inside each canal is endolymph fluid and a sensory region called the crista ampullaris with hair cells embedded in a gelatinous cupula. When the head rotates, the endolymph lags behind due to inertia, bending the cupula and the hair cells. This bending changes the rate at which sensory neurons fire, giving the brain information about the speed and direction of head movement. In contrast, the vestibule houses the utricle and saccule, which detect linear acceleration and, along with gravity, contribute to static equilibrium. The cochlea handles hearing, and the oval window is the membrane through which vibrations enter the inner ear, not a sensor of dynamic movement. So the fluid-filled structures that provide information about dynamic equilibrium are the semicircular canals.

Dynamic equilibrium is sensed by the semicircular canals, a set of fluid-filled channels in the inner ear. Each canal is oriented in a different plane, so they detect rotation around different axes. Inside each canal is endolymph fluid and a sensory region called the crista ampullaris with hair cells embedded in a gelatinous cupula. When the head rotates, the endolymph lags behind due to inertia, bending the cupula and the hair cells. This bending changes the rate at which sensory neurons fire, giving the brain information about the speed and direction of head movement.

In contrast, the vestibule houses the utricle and saccule, which detect linear acceleration and, along with gravity, contribute to static equilibrium. The cochlea handles hearing, and the oval window is the membrane through which vibrations enter the inner ear, not a sensor of dynamic movement. So the fluid-filled structures that provide information about dynamic equilibrium are the semicircular canals.