Evolution of the cochlea of the ear, consisting of the scala media, the scala tympani, and the scala vestibuli. Regarding mammals, placental and marsupial cochleae have similar cochlear responses to auditory stimulation as well as DC resting potentials. This leads to the investigation of the relationship between these therian mammals and researching their ancestral species to trace the origin of the cochlea. This spiral-shaped cochlea that is in both marsupial and placental mammals is traced back to approximately 120 million years ago. The development of the most basic basilar papilla (the auditory organ that later evolved into the Organ of Corti in mammals) happened
Cochlea "helicotrema", due to the stiffness-mediated tonotopy. A very strong movement of the basilar membrane due to very loud noise may cause hair cells to die. This is a common cause of partial hearing loss and is the reason why users of firearms or heavy machinery often wear earmuffs or earplugs. Not only does the cochlea "receive" sound, it "generates" and amplifies sound when it is healthy. Where the organism needs a mechanism to hear very faint sounds, the cochlea amplifies by the reverse transduction of the OHCs, converting electrical signals back to mechanical in a positive-feedback configuration. The OHCs have