ANATOMY

UNIT 1 NOTES:

Hearing & Equilibrium

(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:1. Inside ear

2.Tympanic Membrane (Ear Drum)

3.Hammer, Anvil, Stirrup (3 Bones)

4.Oval Window of Cochlea

5.Fluid within Cochlea

6.Cochlear Nerve and Brain

(2) Cochlea

• Cochlea = Snail like structure in inner Ear.

• Contains receptors for balance and equilibrium.

• Contains receptors for pitch and frequency.

(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

(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.

(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.

(6) Motion Sickness• The result of an inefficient dynamic

equilibrium…– Receptors either too sensitive or too slow at

sending messages

• Cause:– Too many visual messages– Too many inner ear messages– Visual conflicts with Inner Ear

• Unique to each individual

(7) Deafness

• Deaf = Any hearing loss

• Types:– Conduction– Sensorineural

(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

(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