ANATOMY

UNIT 2 NOTES:

Hearing & Equil ibrium

(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

(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.

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

(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

(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