1. Sound Waves Enter the Ear:
- Sound waves travel through the outer ear canal and reach the eardrum, causing it to vibrate.
- These vibrations are then transferred to the tiny bones in the middle ear (malleus, incus, and stapes).
- The stapes, the smallest bone in the body, presses against a membrane called the oval window, which separates the middle ear from the inner ear.
2. Fluid Waves in the Cochlea:
- The pressure from the stapes creates waves in the fluid within the cochlea.
- This fluid movement stimulates tiny hair cells located on a structure called the basilar membrane.
3. Hair Cell Activation and Signal Transduction:
- The hair cells are specialized sensory cells that bend in response to the fluid waves.
- This bending triggers a chemical signal that is converted into an electrical signal.
4. Transmission to the Brain:
- The electrical signals from the hair cells are transmitted to the auditory nerve, which carries the information to the brain.
- The brain interprets these signals as sound.
How the Cochlea Detects Different Frequencies:
- The cochlea is divided into different sections along its length.
- Each section of the basilar membrane is tuned to a specific frequency of sound.
- Higher frequency sounds vibrate the stiffer, narrower end of the basilar membrane, while lower frequency sounds vibrate the wider, more flexible end.
- This tonotopic organization allows the brain to distinguish different pitches.
In Summary:
The cochlea is essential for converting sound vibrations into electrical signals that the brain can interpret as sound. It plays a vital role in hearing, allowing us to perceive different frequencies and pitches.