The ear is designed like a funnel to channel sound waves into the auditory canal and cause the ear drum to vibrate. Inside the ear, the vibrations are transmitted through three small bones to the cochlea, where fluid carries the signal to receptors. The cochlea contains receptors for both hearing and balance. Two types of equilibrium receptors in the cochlea, called the vestibular apparati, help the brain monitor the position of the head. Static equilibrium receptors identify basic positions like up and down, while dynamic equilibrium receptors detect more detailed movement and rotations through fluid in the semicircular canals. Damage to different parts of the ear can cause either conduction or sensorineural deafness.

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