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Neuroscience: Exploring the Brain 4th Edition

Neuroscience: Exploring the Brain (4th Edition)

Book Edition4th Edition
Author(s)Bear, Connors
PublisherWolters Kluwer

Chapter 11, End of Chapter, Review Questions, Exercise 1

Page 412


Cochlea is a portion of the middle ear which contains the spiral organ of Corti which is the receptor organ for hearing. 

It consists of tiny hair cells that translate the fluid vibration of sounds from its surrounding ducts into electrical impulses that are transmitted to the sensory nerves.

The cochlea is made up of three canals, namely, the scala tympani, the scala vestibuli and the scala media.

Cochlea contains the apparatus for transforming the physical motion of the oval window membrane into a neuronal response. The stages of the auditory pathway are:

  • As sound waves enter the ear, they travel through the external ear, the external auditory canal, and strike the eardrum making it vibrate.
  • The focal portion of the eardrum is associated with a little bone of the center ear called the malleus (hammer). As the malleus vibrates, it communicates the sound vibrations to the next two little bones or ossicles of the middle ear, namely, the incus and stapes.
  • The movement of the stapes brings movement in the oval window associated with it which is later transferred to the cochlea, a liquid-filled snail-like structure that contains the receptor organ for hearing.
  • The cochlea contains the spiral organ of Corti, which is the receptor organ for hearing. It comprises small hair cells that decipher the liquid displacement caused by the sound waves into electrical impulses conveyed to the brain by the cochlear nerve.

Verified Answer

The middle ear consists of auditory ossicles, which refers to the three smallest bones: malleus, incus, and stapes. The malleus is located towards the eardrum (connecting external ear to the middle ear) while the stapes is located towards the oval window (connecting middle ear to the inner ear). As the sound waves are produced, they cause vibration of eardrum. These vibrations are transmitted to the malleus and eventually to stapes through incus. As the stapes vibrates to and fro against the oval window, it communicates soundwaves through the liquid of the cochlea. Thus the vibrations of the ossicles leads to displacement of cochlear fluid and movement of hair cells present in the organ of corti to produce nerve signals.

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