1. ANATOMY
UNIT 2
NOTES:
Hearing &
Equilibrium

2. (1) Ear Design
• Ear is a well designed funnel:
– Sound waves spiral down into auditory canal.
– Sound Waves smack against ear drum (tympanic
membrane).
• Sound Path:
– Inside ear
– Tympanic Membrane (Ear Drum)
– Hammer, Anvil, Stirrup (3 Bones)
– Oval Window of Cochlea
– Fluid within Cochlea
– Cochlear Nerve and Brain

5. (2) Cochlea
• Cochlea = Snail like structure in inner Ear.
• Contains receptors for balance and
equilibrium.
• Contains receptors for pitch and frequency.

8. (3) Equilibrium & Balance
• Your ears keep track of your body’s
position.
• Equilibrium receptors lie within the cochlea
(they are called the Vestibular Apparati).
• 2 Types of Equilibrium:
– Static
– Dynamic

9. (4) Static Equilibrium
• Static = Tells brain the basic position of
head.
– Up, Down, Left, Right, Forward, Back
• Uses Receptors called the Macuale:
– On top of maculae lies the otolithic membrane
(gel-like membrane)
– When Head Moves  Otoliths Move!
– Movement of otoliths places pressure on
maculae, sending message through vestibular
nerve to brain.

11. (5) Dynamic Equilibrium
• Dynamic = Tells brain the more detailed
positioning and movement of the head.
– Rotations and Angles
• Uses the Semicircular Canals of Cochlea:
– Contain channels called Crista Ampullari.
– Crista Ampullari contain receptor cells,
endolymph fluid and a capula cap.
– When head turns, fluid pushes against capula
cap, stimulating receptors, and sending
message to brain.

13. http://www.youtube.com/watch?v=vTiGskc1o48

14. (8) Motion Sickness
• The result of an inefficient dynamic
equilibrium…
– Semicircular Canals either too sensitive or too
slow at sending messages
• Too many visual messages
• Too many inner ear messages
• Visual conflicts with Inner Ear
• Unique to each individual

15. (7) Deafness
• Deaf = Any hearing loss
• Types:
– Conduction
– Sensorineural

16. (8) Conduction Deafness
• Something Blocks Tympanic Membrane
• Sound Waves cannot reach Ear Drum +
Inner Ear
• Causes:
– Ear Wax
– Ruptured Ear Drum
– Injured Hammer, Anvil and/or Stirrup
• Usually Temporary, Solved by Surgery

17. (9) Sensorineural Deafness
• Damage to actual parts of ears:
– Receptor Cells
– Cochlea
– Vestibular Nerve
• Can be hereditary, damage from
disease/virus, damage from loud noises
• Often permanent