Auditory Tracts (Dennis) Flashcards
Where do cochlear fibers enter into the brainstem?
Cerebellopontine angle
How is auditory information received in the CNS
Fibers of the cochlear nerve (CN VIII) synapse in the cochlear nucleus. Fibers then split into ascending and descending bundles
Where do the ascending and descending bundles of primary afferent CN VIII synapse?
- Ascending Bundle: Anterior subdivison of anterior/ventral cochlear nucleus
- Descending Bundle: Posterior subdvision of anterior/ventral cochlear nucleus and posterior part of posterior cochlear nucleus
How is the cochlear nucleus distributed
- Posterior/dorsal cochlear nucleus
- Anterior/ventral cochlear nucleus
- Anterior part
- Posterior part
What is the function of the monaural tract?
Information about sounds at a single ear routed to contralateral side
Where are the primary cell bodies located in the monaural tracts?
Posterior/Dorsal Cochlear Nucleus in the Medulla
Where does the monaural tract cross to the contralateral side?
Pons via posterior/dorsal acoustic stria
What are the points of synapse in the monaural tracts?
- Inferior Colliculus
- Medial Geniculate Nucleus
- Layer IV of Primary Auditory Cortex (Heschl’s Gyrus)
What is the Route of the Monaural Tract
- Fibers ascend from the posterior cochlear nucleus (medulla) and travel contralateral through the posterior acoustic stria.
- Fibers then ascend through the lateral lemniscus and synapse at the inferior colliculus (midbrain).
- Fibers then ascend through the branchium of the inferior colliculus and synapse at the medial geniculate nucleus (thalamus).
- Fibers then finish by synapsing at the primary auditory cortex.
What is the function of the binaural tract?
Manages information about differences between sounds at both ears
Role in localization of sound
What are the points of synapse of the binaural tract?
- Superior Olivary Nucleus
- Inferior Colliculus
- Medial Geniculate Nucleus
- Layer IV of Primary Auditory Cortex (Heschl’s Gyrus)
Where are the primary cell bodies for the Binural Tract and where do they synapse
Anterior Cochlear Nucleus
Synapse at both the Ipsilateral and Contralateral superior olivary complex
What structure does the binaural fibers pass through to reach the contralateral superior olivary complex?
Trapezoid body in the pons
Where is the first place that information from both ears converge
Superior Olivary Nucleus
Divided into medial & lateral parts
What input does the Medial Superior olivary nucleus receive
Receives excitatory input from both the ipsilateral and contralateral anterior cochlear nucleus of both ears
What input does the lateral superior olivary nucleus receive?
Excitatory input from ipsilateral anterior cochlear nucleus and inhibitory input from contralateral anterior cochlear nucleus
Fibers from the medial and lateral superior olivary nuclei ascendind and syanpse ______, then ascend further to synapse at the ________
Lateral leminiscus
inferior colliculus
Where does the central nucleus of the lateral leminiscus send fibers
Inferior colliculus