sit in the cochlear wall of the fluid-filled inner ear. The inner ear has upper and lower portions. The upper portion of the inner ear has three loops called the semicircular canals and two chambers called the utriculus and the sacculus. The upper portion of the inner ear helps organisms maintain their sense of equilibrium or balance. Changes in the position of the head cause calcium carbonate crystals to shift on their bed of sensory hairs in the utriculus and the sacculus. The changes as to which hairs are being stimulated by the presence of crystals are reported to the cerebellum which, then, translates the information into knowledge of the position of the head relative to gravity. The lower portion of the inner ear, called the cochlea, is the organ of hearing. The coiled tube, snail-like in appearance, contains three canals. The vestibular canal runs from the oval window to the tympanic canal which, in turn, runs to the round window. The cochlear canal is sandwiched in between the vestibular and tympanic canals. The receptor cells for sound, specialized for the detection of vibration, are contained within the organ of Corti. This organ projects out into the cochlear canal from the canal's basilar membrane. Each receptor cell has a sensory hair at its apex which projects into the gelatinous tectorial membrane. Dendrites of sensor neurons are in close contact with the
surface of each receptor cell.
The reception of vibration by the ear begins with the passage of vibrations carried in the air down the auditory canal causing the tympanic membrane to vibrate at the
