Anatomy of the Ear and Equilibrium

Ear Structure and Function

• The eardrum (tympanic membrane) vibrates with sound waves.
• Ossicles:
  • Malleus (first bone),
  • Incus (second bone),
  • Stapes (connects to the cochlea via the oval window).
• Eustachian tube is responsible for draining mucus; blockage leads to fluid buildup.

Cochlea and Hair Cells

• Cochlea contains hair cells in endolymph.
• Sound waves cause cells to create nerve impulses.

Vestibule and Equilibrium

• Vestibule controls equilibrium; involves:
  • Static equilibrium: Detects stillness and head position.
  • Dynamic equilibrium: Detects movement (e.g., head turns or spins).
• Ear stones (otoliths) in gel substance activate hair cells to inform brain of head position.

Semicircular Canals

• Three canals (anterior, posterior, lateral) detect motion:
  • Anterior: head-over-heels motions.
  • Posterior: for tilting movements.
  • Lateral: for spinning motions.
• Fluid movement in canals signals head movement via hair cells.

Nervous System Interaction

• Vestibulocochlear nerve is responsible for transmitting signals from cochlea and vestibule to the brain.
• Conflicting signals (from eyes and inner ear) can lead to dizziness or motion sickness.