Lecture 1: Auditory Tracts Flashcards
Where do the primary afferents from the cochlear division of CN VIII enter the brainstem?
Considered 1st order neuron
Pontomedullary junction
Where do the ascending and descending bundles of primary afferent CN VIII synapse?
- Ascending Bundle: Anterior subdivison of ventral cochlear nucleus
- Descending Bundle: Posterior subdvision of ventral cochlear nucleus and dorsal cochlear nucleus
What is the function of the dorsal cochlear nuclei?
- Identifying sound source elevation
- Identifying complex spectral characteristics of sound
What is the function of the ventral cochlear nucleus?
Horizontal localization of sound
What is the function of the monaural tract?
Information about sounds at a single ear
Where are the primary cell bodies located in the monaural tracts?
Dorsal Cochlear Nucleus
Where does the monaural tract cross to the contralateral side?
Pons via 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)
Fibers from the monaural tract travel through what part of the internal capsule to reach the primary auditory cortex?
Sublenticular limb of the internal capsule
What is the function of the binaural tract?
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)
What structure does the binaural fibers pass through to reach the super olivary complex?
Trapezoid body in the pons
What is conduction deafness?
How can that occur?
Obstructed or altered transformation of sound external and middle ear
- Damage/Infection to tympanic membrane
- Damage to ossicles
- Build up of earwax
What is sensorineural deafness?
How does it occur?
Ipsilateral deafness due to damage in the inner ear
- Damage to cochlea
- Hair Cells
- Spiral Ganglion Cells
- Damage to cochlear part of CN VIII
- Damage to cochlear nuclei
What is central deafness?
What is its symptoms?
Theoretically not deaf but there is damage to central pathways (past superior olivary complex)
- Cannot localize sound
- Hard to follow conversations in noisy areas
What supplies the cochlea and auditory nuclei of pons and medulla?
Basilar Artery
Occlusion of what branch of the Basilar Artery will cause monaural hearing loss?
AICA
Can also damage Facial Nerve