Main Function:
- Transforms sound waves into electrical signals that the brain can interpret.
Parts:
- Cochlea: A spiral-shaped, fluid-filled chamber.
- Oval window: A membrane separating the middle ear from the cochlea.
- Round window: Another membrane that allows pressure release in the cochlea.
- Cochlear duct: A fluid-filled channel within the cochlea that contains hair cells.
- Hair cells: Sensory cells with tiny hairs that respond to sound waves.
- Tip links: Structures connecting hair cells that open ion channels when bent.
How it Works:
- Sound waves vibrate the stapes bone in the middle ear.
- The stapes pushes on the oval window, creating a pressure wave in the cochlear fluid.
- The pressure wave travels through the cochlea, causing the basilar membrane (the floor of the cochlear duct) to vibrate.
- Different frequencies of sound waves cause the basilar membrane to vibrate at different locations.
- Hair cells rest on the basilar membrane and are stimulated by its movement.
- When a hair cell is stimulated, its tip links bend, opening ion channels and generating an electrical signal.
- The electrical signal travels through the auditory nerve to the brain, where it is interpreted as sound.
Additional Points:
- The cochlea acts like a prism for sound waves, separating different frequencies and sending them to different locations on the basilar membrane.
- The hair cell response is very fast due to the direct connection between tip links and ion channels.
- This lecture covers the basic mechanism of sound detection in the cochlea. The next lecture will discuss the cochlear amplifier, which enhances the weak signal from the hair cells. Cochlear Amplifier