auditory lec 3

Question 1

2 major divisions of inner ear?

Answer 1

1. vestibular division
2. cochlear division

Question 2

what is the modiolus? (2)

Answer 2

• central axis of the cochlea
• consists of spongy bone + contains the cochlear nerve

Question 3

bony labyrinth: what is the osseous spiral lamina? how does the habenula perforata relate?

Answer 3

• osseous spiral lamina: projects from modiolus in between the scala vestibuli and scala tympani
• habenula perforata: perforations in osseus spiral lamina to allow fibers of vestibulocochlear nerve thru

Question 3

membranous labyrinth: what is the scala vestibula vs media vs tympani? what about the helicotrema?

Answer 3

• scala vestibuli: upper canal, contains perilymph
• scala media (aka cochlear duct): continuous w/ semicircular canals + contains ENDOlymph
• scala tympani: lower canal, also contains perilymph
• helicotrema: at apex of cochlea, connects scala vestibuli and tympani

Question 4

which scala connects to the round window? oval window?

Answer 4

• round window: scala tympani
• oVal window: scala Vestibuli

Question 5

which is bigger, the oval or round window?

Answer 5

• oval window is bigger

Question 6

where is the reissner membrane? basilar membrane?

Answer 6

• reissner: between scala vestibuli + scala media
• basilar: between scala media and scala tympani

Question 7

how is the basilar membrane different at the base vs apex of the cochlea?

Answer 7

• base: stiff and narrow – tunes high frequencies
• apex: loose and floppy – tunes low frequencies

Question 8

where is the organ of corti? what does it contain?

Answer 8

• sits on basilar membrane
• contains IHCs and OHCs

Question 9

is there more OHCs or IHCs?

Answer 9

• more OHCs
• 3:1 OHCs: IHCs

Question 10

what are stereocilia? what are they connected by?

Answer 10

• hairlike structures on the OHCs and IHCs
• connected by tip links and cross links

Question 11

describe the path which vibrations of sound travel thru in the inner ear (3)

Answer 11

1. stapes vibrates at oval window
2. pressure waves pass thru scala vestibuli and scala tympani, ending at round window
3. simultaneously, this causes motion of the basilar membrane, the organ of corti, the tectorial membrane, and the hair cells

Question 12

T or F: kinocilia exist in the vestibular system only

Answer 12

true

Question 13

T or F: only OHCs have stereocilia embedded in the tectorial membrane

Answer 13

false – both IHCs and OHCs

Question 14

how are stereocilia organized? when does greater vs reduced excitation occur in relation to their position?

Answer 14

• organized from taller to smaller
• depolarization (+excitation) = when bending to tallest
• hyperpolarization (-excitation) = when bending to shortest

Question 15

what is the innervation of the OHCs?

Answer 15

• afferent (sensory): vestibulocochlear nerve (via internal auditory canal) to brain
• efferent (motor): amplify motion of basilar membrane, increase sensitivity to lower frequencies, and protect from over-exposure to loud noise

Question 16

what is the innervation of the IHCs?

Answer 16

afferent (sensory) only

Question 17

which type of hair cells have “W” pattern stereocilia?

Answer 17

OHCs