Afferent Auditory Pathway Flashcards
What is the first order neuron’s course?
From the base of the hair cells, exit the habenula perforata joining together to form spiral ganglion, then courses to the modiolus and exits cochlea to enter the Internal Auditory Meatus.
Where does the first order neuron terminate?
In the cochlear nucleus with the second order neurons.
What forms the core of the nerve?
The most apical fibers. Low f.
What forms the periphery of the nerve? How?
The basal fibers- added in a twisted fashion to form the periphery of the nerve. High f
Which fibers are most exposed? What does this mean?
High frequency fibers are the most exposed and therefore more subject to trauma.
What are the major tracts of the ascending auditory pathway/What is it’s course?
Cochlear nerve enters the IAM and is joined by the two divisions of the vestibular nerve to complete the VIIIth nerve. Then courses toward the brainstem, specifically the cochlear nucleus. Half of neurons cross the median plane and synapse at superior olivary nucleus, half stay same side. The neurons then travel superiorly from superior olivary nucleus to form the lateral lemniscus tract. Then some synapse and some travel to the inferior colliculus of the midbrain. Some decussate from one side to the other again. Then course through or synapse at the medial geniculate nuclei/thalamic nucleus of auditory pathway. Finally will course through and terminate in auditory cortex/temp lobe/Heschl’s gyrus.
Why does the cerebral auditory cortex receive input primarily from the contralateral ear via the ipsilateral medial geniculate nuclei?
Because of decussating nerve fibers.
What is the tonotopic organization of the afferent pathway?
Orderly correspondence between the cochlea and acoustic projection on the cerebral cortex, which means frequency related spatial distribution of cochlea and cochlear nerve is maintained through the central auditory pathway to the cortex.
What is the final structure in the auditory periphery?
The auditory nerve.
