Inner ear. Illustration of the sensory organs of the human inner ear. The inner ear contains a maze of fluid-filled passages called the labyrinth, shown here in blue. At right is the cochlea, a hollow spiral containing microscopic hairs that respond to sound vibrations conveyed from the mid- dle ear. The near end of the spiral picks up high- frequency sound; the central (far) end detects low frequency sound. Nerves (yellow) connected to the cochlea carry sound impulses to the brain. The three loops at left are the semi-circular canals. These provide the sense of balance by detecting movement of fluid through the three planes.