Auditory System

Question 1

Compartments of the ear

Answer 1

Outer - mechanical
Middle - mechanical and amplify
Inner - neuro

Question 2

Cochlear duct

Answer 2

Houses hair cells and filled wiht endolymph

Surrounded by bony ducts (vestbular on top and tympanic on the bottom)

Question 3

Sound path

Answer 3

Tympanic mmb
Malleus
Incus
Stapes
Oval window 
Through ducts to round rindow

Question 4

Membranes

Answer 4

Basilar on bottom of cochlear separates from tympanic duct

Vestbiular on top of cochlear separates form vestbiular duct

Question 5

Hair cells

Answer 5

K+ moves into open membranes to depolarize

Results in NT release

Also efferent compoennts that tunes

Question 6

Cochlea location

Answer 6

In the petrous protion of the temporal bone

CN8 and 7 travle through internal auditory meatus to go to brainstem

Question 7

Spiral ganglion

Answer 7

Cell bodies of the sensory bipolar neurons…sit in the organ of corit

Question 8

Modiolus

Answer 8

Protects deep portion of the cochlea and spiral ganglion

Question 9

Stria vascularis

Answer 9

Leaches endolymph into cochlear duct

Question 10

Basilar membrane movement

Answer 10

Hair cells rub against tectorial membrane which depolarizes bipolar neurons

Question 11

Frequency differentiation

Answer 11

Closer to oval window - higher freuqncy…rigid at base and higher freuqneyc sounds more attentuated by distance

Closer to apex - lower frequency

Question 12

Pontomeduallary junction

Answer 12

Ventral cochlear nucleus contributes to sound localization…both unconscious (superior olive) and conscious (cortex)

Dorsal cochlear nucles…primarily to sound processes like sound discrimination (cortex)

Sound represented bilaterally but there is contralateral over-representation

Question 13

Superior olive

Answer 13

Medial uses time difference for LF sounds

Lateral uses amplitude differences for HF sounds…nucleus of trapeoid body also involved

Question 14

Dorsal acoustic fibers

Answer 14

Ascend in the lateral lemnicus to the inferior colliculus

Fibers from SO and NTB also ascend in lateral lemniscus

Question 15

Dampening loud sounds

Answer 15

Both pathways originate in superior olive nucleus

Stapedius muscle from CN7

Tensor tympani from CN5

Question 16

Midbrain

Answer 16

Fibers in lateral lemniscus synapse in the IC

Also a commisure of the IC…fibers pass from brachium of the IC to the medial geniculate nucleus of the thalamus

Question 17

Thalamus and cortex

Answer 17

Fibers from IC synapse on MGN

MGN relays precise information to PAC

Fibers from MGN to PAC called auditory radiations

Question 18

PAC and Wernick’s area

Answer 18

PAC - conscious sound detection and localization and discrimination…lower in lateral and higher in medial

Wernick’es - on left side…speech disrcimination

Question 19

Types of conductive hearing loss

Answer 19

Otitis media
Tympanic membrane perforation
Otoscelrosis - bone growht between temorla bone and stapes…reduces mobility and therefore condcuton

Most form some kind of occlusion in middle ear

Question 20

Sensory hearing loss

Answer 20

Damage to hair cells

Acoustic neuroma

Question 21

Non-specific disorders

Answer 21

Tinnitus - could be any reason…even PTSD

Question 22

Weber test

Answer 22

Bone conduction in each ear simultaneously

If louder in affected ear, then conductive

If quieter in affected ear, then sensory

Question 23

Rinne test

Answer 23

Tests air conduction versus bone conduction in each ear

Hearing sound louder through bone suggests conduction loss in ear

Hearing sound louder through air in each ear but louder in one than other sugests sensory

Question 24

Unilateral lesion of cochlea or CN 8

Answer 24

Unilateral deafness

Question 25

Unilateral lesion of auditory pathway

Answer 25

PICA

Bilateral hearing reduction but not deafness

Question 26

Unilateral cortical lesion

Answer 26

MCA lesion

Decrease in ability to consciously discriminate sounds

Question 27

Wernicke leison

Answer 27

Inability to understand language