Neuroanatomy Exam 2 - Auditory

What makes up the external ear?

auricle/pinna

What makes up the middle ear?

- tympanic membrane
- 3 bones/ossicles

What is the eardrum?

tympanic membrane

What makes up the inner ear?

cochlea

How many chambers does the cochlea have?

3 chambers

What are the 3 chambers?

- scala vestibuli
- scala media/cochlear duct
- scala tympani

What does the Scala media contain?

organ of corti

What does the organ of corti contain?

hair cells innervated by cochlear ganglion axons - cochlear branch of CNVIII

What does the basilar membrane do?

separate the cochlea into upper and lower chamber

Upper chamber

- scala vestibuli
- scala media

Lower chamber

scala tympani

Base

skinny and stiff (detects high frequencies)

Apex

wider and floppy (low frequency)

Auditory pathway

sound waves, vibrates tympanic membrane and ossicles, moves fluid and basilar membrane and activates hair cells

Where is the cell body of neuron 1?

cochlear ganglion

Where does neuron 1 synapse?

cochlear nucleus in pontomedullary junction

Where is the cell body of neuron 2?

cochlear nucleus in pontomedullary junction

The basilar membrane has specific areas that respond to specific frequencies, what is that called?

tonotopic arrangement

Where does auditory pathway start?

CN VIII and pontomedullary junction

True/False
Most axons will cross, but some will stay ipsilateral.

true

Where do they ascend?

lateral lemniscus

Where do they synapse?

inferior colliculus and crosstalk

True/False
Auditory pathway is unusual in bilateral ascent.

true

Due to bilateral ascent, no conversational hearing deficits with unilateral CNS lesion, except at the _____

pontomedullary

Conductive hearing deficits

when transmission of vibrations is prevented

Sensorineural hearing deficits

damage to receptor cells or CN VIII

What is acoustic neuroma?

when noncancerous slow growing tumors grow along CN VIII