Auditory System

Question 1

If you have a lesion where this pointer is will you have unilateral easily detectable deafness?

Answer 1

No- because there is representation of information in both ears in both nuclei

-might have some subtle decrease but not a dramatic loss

Question 2

If you have damagage in the cochlea say that hair cells die–will you have unilateral deafness?

a lesion of the spinal ganglion?

a lesion Cochlea nuclei?

Answer 2

Yes!

• because the represesntation for each ear is only represented on one side
• if you have lesion there towards peripheral it is unilateral deafness
• if they have unilateral deafness you know its in the periphery part of the ear

Question 3

Map the signal pathway in auditory system

Answer 3

-major fiber bundle-lateral leminiscus

• conveys auditory information from brainstems structures
  
  • like from the superior olivary complex
• Conveys information to the midbrain (mesencephalon)
  
  • the marker that tells you it is the midbrain is the cerebral aquaduct
• lateral leminiscus sends info to the inferior colliculus of the dorsal side of the midbrain
  
  • they are receiving BILATERAL information via the lateral leminiscus
• then cells in the inferior colliculus project to the medial geniculate nucleus in the thalamus
  
  • what is the unlabeled space ther (3rd ventricle)
  • these cells have a group axons from the inferior colliculus to the medial geniculate and this is called the Brachium of inferior colliculus
• cell bodies within the medial geniculate nucleus (in the diencephalon (thalamus)) project to the cerebral cortex to the area called acoustic area of temporal lobe

Question 4

What colors are what tones?

Answer 4

Question 5

What are the differences in sound frequency between these three points from base to the apex?

Answer 5

Question 6

Where are the cell bodies of the auditory nerve contained?

Answer 6

Within the spiral ganglion

-the auditory component of the CN VIII terminates in ipsilateral cochlear nuclei

Question 7

What is a big marker for Pons?

Answer 7

CN V

Question 8

Where are the cochlear nuclei located within the rostral medulla?

Answer 8

They are located dorsally and laterally

Question 9

The cochlear nuclei project to the superior olivary nucleus, nuclei of the lateral leminiscus and inferior colliculus

• Most axons are originating in the cochlear nuclei cross to the contralateral side via the: ______, _______, _______
• there are also ipsilateral projections

Answer 9

• Dorsal acoustic stria
• intermediate acoustic stria
• trapezoid body

Question 10

What are some implications of bilateral projections for detection deafness?

Answer 10

• a deafness is usually detected if the damage is at the level of the cochlear nuclei or before, e.g. cranial nerve VIII or inner ear
• Lesions of the auditory system rostral to the cochlear nuclei are less likely to be detected by auditory testing

Question 11

The lateral lemniscus projects to the inferior colliculus of the midbrain

• The lateral lemniscus includes axons which originate in the:
  
  • ______
  • _______
  • _______
• the lateral lemniscus travels within the ________ to the _______

Answer 11

• 1) Dorsal cochlear nuclues
• 2) Superior cochlear nucleus
• 3) Nucleus of the later lemniscus
• The lateral lemniscus travels within the dorsal lateral pons to the inferior colliculus

Question 12

what is lemniscus another word for?

Answer 12

group of axons

Question 13

the inferior colliculus projects to the _____ via the branchium of the inferior colliculus

Answer 13

Medial geniculate nucleus

• does auditory information
• MGN is in the thalamus and sends its axons to the cerebral cortex

Question 14

The auditory radiations of the MGN terminate in what part of the cerebral cortex?

Answer 14

Temporal lobe