Neuroscience: The Cochlea

Overview

• The cochlea is a crucial structure in the inner ear involved in the process of hearing.
• Sound waves travel through the ear canal, vibrate the tympanic membrane (eardrum), and prompt movement in the ossicles (tiny bones).
• These vibrations are transmitted to the oval window, located in the cochlea.

Structure of the Cochlea

• Shape: Resembles a snail shell.
• Interior: Consists of three fluid-filled canals:
  • Scala vestibuli
  • Scala media
  • Scala tympani
• Fluids:
  • Scala vestibuli and scala tympani contain perilymph.
  • Scala media contains endolymph.

Function and Process

• When the oval window is depressed, it creates waves in the cochlear fluid.
• These waves cause movement in the basilar membrane.
• Visualizing the cochlea uncoiled helps understand the wave movement through the basilar membrane.

Basilar Membrane

• Different sections respond to different sound frequencies.
• Waves peak at parts of the membrane that correspond to the sound frequency.
• Translates sound frequencies into neural activity.

Organ of Corti

• Sits atop the basilar membrane.
• Contains receptor cells known as hair cells, named for stereocilia protruding from them.

Hair Cells and Signal Transduction

• Vibration of basilar membrane moves hair cells and stereocilia.
• Movement of stereocilia opens ion channels, releasing neurotransmitters.
• Signals propagate to the vestibulocochlear nerve.
• The auditory stimulus is then carried to the brain for analysis and perception.