How Sound Travels to the Brain

Overview

• The process of sound traveling from its source to the brain.

Sound Wave Generation

• Example: Trumpet playing.
• Sound waves are created in the air when an instrument is played.

Ear Anatomy and Sound Processing

1. Outer Ear

   • Catches sound waves.
   • Directs them through the ear canal.

2. Eardrum

   • Membrane about half the size of a dime.
   • Vibrates when sound waves reach it.

3. Ossicles

   • Three tiny bones: malleus, incus, and stapes.
   • Functions: Amplify sound vibrations and transfer them to the cochlea.

4. Cochlea

   • Shape: Snail-like, size of a garden pea.
   • Filled with fluid; vibrations create ripples in this fluid.

5. Hair Cells and Stereocilia

   • Hair-like structures called stereocilia are on top of hair cells.
   • Hair cells ride the fluid waves in the cochlea.
   • Movement of hair bundles turns vibrations into electrical signals.

Signal Transmission to the Brain

• Ions rush into hair cells during movement.
• Chemicals are released at the bottom of hair cells, binding to auditory nerve cells.
• Electrical signals travel along the auditory nerve to the brain.

Frequency Detection

• Different hair cells respond to different sound frequencies:
  • Base of cochlea: Detects higher pitched sounds (e.g., piccolo, flute).
  • Top of the cochlea: Detects lower pitched sounds (e.g., trumpet, trombone).
  • Apex of cochlea: Detects the lowest pitched sounds (e.g., tuba).

Brain Interpretation

• The brain interprets electrical signals as recognizable sounds.