Into the Labyrinth

The cochlear duct houses the organ of Corti which is where hearing actually takes place

The duct itself divides the bony cochlea into upper and lower sections; the upper section being the scala vestibuli and the lower section is the scala tympani. Dividing the cochlear duct and the scala vestibuli is the vestibular membrane or Reissner’s membrane. The basilar membrane is the floor of the cochlear duct.
Perilymph (similar to CSF) fills the scala tympani and scala vestibuli; endolymph fills the cochlear duct
The organ of Corti rests on the basilar membrane, and consists of hair cells, the tectorial membrane, and supporting cells

Pitch is the frequency of the sound waves
Sound waves must be of sufficient amplitude to vibrate the eardrum, and have a frequency capable of stimulating the hair cells

Because the basilar membrane is not the same thickness throughout the cochlear duct, different frequencies will cause the basilar membrane to vibrate and bulge upward at different places along its length
Higher frequencies will cause the narrower portion of the basilar membrane (near the oval window) to vibrate
Lower frequencies vibrate the area furthest away from the oval window (the thicker areas)
When an area of the basilar membrane moves, those hair cells respond to the movement and a particular pitch is perceived
The higher upward the bulging of the basilar membrane, the greater the perceived loudness
The perception of sound starts when waves vibrate the eardrum, which transmits the motion to the malleus. The malleus vibrates against the incus, which in turn moves the stapes. The movement of the stapes against the oval window creates ripples in the perilymph and endolymph, which causes deformation of the basilar membrane. The ripples continue through the perilymph and endolymph until they end against the round window (located just below the oval window).

Static equilibrium is sensing where the head is, relative to gravity, or to sense acceleration or deceleration
Dynamic equilibrium is needed to maintain balance when the head or body is rotated or moved suddenly

The macula of the ear is a small, highly specialized area of epithelium located in the utricle and saccule.
Within the matrix of the macula are otoliths, which are suspended within a gelatin-like material on top of macular hair cells.
The utricle and the saccule are located at 90 degree angles to each other; the utricle is parallel to the base of the skull and the saccule is perpendicular
Stimulation of the maculae evokes righting reflexes, which basically means that if you sense a loss of equilibrium, you will automatically try to right yourself (like if you slip, or fall)

Dynamic equilibrium is sensed via the crista ampullaris in the semicircular canals

It is similar to the maculae of the ear
The crista ampullaris is cone-shaped, with many hair cells that have their processes located in the cupula

The cupula is a gelatinous cap that is like a float in the endolymph; when the endolymph moves, the cupula is moved, and the hair cells are stimulated