Auditory and Vestibular Pathways Flashcards
Where do auditory afferents project?
Dorsal and ventral cochlear nuclei
Rostral medulla
Where do the cochlear nuclei project?
Lateral lemniscus
Bilaterally to the superior olivary nuclei
What is the function of the superior olivary nucleus and where does it project?
Compare the arrival time of sound waves and relative intensities
Make an important contribution to the horizontal localization of sounds
Enters the lateral lemniscus and projects to the inferior colliculus
What is the function of the inferior colliculus?
Relay from the lateral lemniscus to the medial geniculate nucleus
Assists in sound localization, acoustic startle reflex, and multisensory integration
What is the function of the medial geniculate nucleus?
Relays information from the inferior colliculus to the primary auditory cortex
Describe the pathway/function of the acoustic reflex
Cochlear nuclei connect to the facial and trigeminal motor nuclei
Some neurons in the SON project back through CN VIII to innervate auditory hair cells
This provides feedback to enhance or inhibit hair cell function to improve sound discrimination
What are the only lesions that can cause unilateral hearing loss?
Cochlear nuclei, CN VIII, the cohclea, or middle or outer ear
Above the cochlear nuclei, the auditory pathways are bilateral
Describe the vestibular pathway
Vestibular afferents project unilaterally tot he vestibular nuclei
VN project to the vestibulocerebellum and descend the medial longitudinal fasiculus to reach spinal levels
Some VN neurons ascend the medial longitudinal fasciculus to reach nuclei of CNs III, IV, VI
And some VN neurons go to the thalamus
Describe vestibular input to the cerebellum
Receive relayed input from the vestibular nuclei and direct input from vestibular afferents via a portion of the inferior peduncle
What is the function of vestibular nuclei projections to CNs III, IV, and VI?
Input to the LMNs for extraocular muscles
Vestibulo-ocular reflexes
What is the function of vestibular nuclei projections that descend to the spine?
Maintain posture against gravity
What are the common peripheral causes of vetigo?
Benign paroxysmal positional vertigo (displaced otoliths)
Meniere’s disease - excessive endolymph pressure
Vestibular neuritis (labyrinthitits) due to inflammation
Vestibular schwannoma - Schwann cell tumor affecting CN VIII
