Lecture 43 4/29/24 Flashcards
What is the function of the stria vasculare?
makes the endolymph for the cochlea
What are the characteristics of the organ of Corti?
-sits on basilar membrane
-hairs come up to tectorial membrane
Which structures are present within the cochlea?
-scala vestibuli
-scala media
-scala tympani
-tectorial membrane
-basilar membrane
-vestibular membrane
-organ of Corti
What happens in the organ of Corti that allows for louder sounds to be perceived?
-higher amplitude sound wave causes more movement of the basilar membrane
-increased basilar membrane movement triggers more hair cells
-the more hair cells triggered, the louder the noise
What are the characteristics of the basilar membrane near the oval window?
-“base”
-narrow
-stiff
-greater movement with high frequency sound waves
What are the characteristics of the basilar membrane far from the oval window?
-“apex”
-wide
-flexible
-greater movement with low frequency sound waves
What is tonotopic organization?
-brain can tell where along the basilar membrane the triggered hair cells are located
-helps with determining high vs low frequency
What is the role of the spiral ganglion?
receive input from the tectorial membrane and transmit it to the brain
What is the relationship between number of coils in the cochlea and the range of sounds heard?
the greater the number of coils, the greater the range of frequencies heard
How does ear position impact ability to hear sound?
ears that are closer together on the skull are able to hear higher frequency sounds
What are the potential diseases of the inner ear?
-labyrinthitis/otitis interna
-noise-induced degeneration
-age-induced degeneration
-chemical degeneration
-cochlear dysgenesis/agenesis
What is sensorineural deafness?
deafness due to the inability of the inner ear to process sound
What can cause sensorineural deafness?
-disease of inner ear
-congenital problems of inner ear
How does treatment differ between degeneration disease and genetic cochlear disease?
-degeneration disease treated with hearing aids
-genetic cochlear disease treated with cochlear implant
What is the auditory cortex?
part of the cerebral cortex where the conscious perception of sound occurs
How is sound processed in the brain, based on which ear heard it?
-left auditory cortex processes sound heard in right ear, and vice versa
Why is hearing considered a learned response?
the temporal lobe learns patterns of sounds
What are the characteristics of albinotic deafness?
-associated with decreased pigmentation
-due to failure of neural crest cell migration; lack of stria vasculare
-unable to produce endolymph in cochlea
What are the characteristics of abiotrophic deafness?
-spontaneous death of sensory hair cells after normal development
-later onset than albinotic deafness
-super rare form
How can hearing be assessed?
-physical exam
-behavioral responses
-electrodiagnostics
How is the inner ear formed?
invagination of ectoderm to form the otic vesicle, which becomes the inner ear
Which type of embryologic tissue forms the tympanic cavity?
endoderm
Which type of embryologic tissue forms the middle ear ossicles?
mesoderm
Which type of embryologic tissue forms the external ear canal?
ectoderm
How does the cochlea work?
-sound waves first move through the scala vestibuli
-turn around and move through scala tympani
-sound waves in scala tympani are able to move the basilar membrane and activate organ of Corti
-hair cells in the organ of Corti come up to the tectorial membrane and can transmit to the membrane when sound waves cause movement in the hair cells