Week 2

Question 1

Cochlea

Answer 1

Connected to the cochlear branch of CN VIII

Responsible for hearing

Filled with perilymph

Question 2

Vestibular system

Answer 2

Connected to the vestibular branch of CN VIII

Balance

Filled with perilymph

Question 3

Cochlea structure

Answer 3

33 mm long, chickpea size structure resembling a snail shell

Coiled 2 1/2 times

Two membranes (reissner & basilar) divide its diameter into three chambers

Question 4

3 chambers of cochlea

Answer 4

Scala vestibuli
Scala media
Scala tympani

Scala vestibuli separated from Scala media by reissner membrane

Scala vestibuli and Scala tympani are connected at Apex through helicotrima

Both scala vestibuli and Scala tympani contain perilymph

Question 5

Basilar membrane structure

Answer 5

Bridge inside a tunnel

Five times wider at the Apex than the base

Structure allows each segment of it to vibrate at its own frequencies

Apex detects lowest frequencies and base detects highest frequencies

Question 6

Organ of Corti

Answer 6

Structure located inside Scala media, on top of the Basilar Membrane

Bridge inside a tunnel

Bounded by a bony shelf on either side (osseous spiral lamina)

Question 7

Organ of Corti consists of:

Answer 7

Basilar membrane
Tectorial membrane
Hair cells
Nerve fibers
Tunnel of Corti

Question 8

Auditory transduction

Answer 8

Same vibration from the tympanic membrane goes through the ossicles

Middle ear structures convert acoustic energy into mechanical energy

Stapes moved into oval window, compressing the perilymph within the Scala vestibuli

Deflects the reissner membrane

Question 9

Auditory transduction continue

Answer 9

Deflection of the reissner membrane causes compression of fluid within the Scala media

Which caused deflection of basilar membrane and tectorial membrane

Hair cells are deflected and convert hydraulic energy into neural energy

Movement is transferred to central nerve 8 nerve fibers, which carries the signal to brain stem structures

Question 10

Cochlea (hair cells) structure:

Answer 10

Each cochlea contains around 15,000 hair cells in 4 rows

Around 50 stereocilia arise out of each hair cell

An inner hair cell connects with 2 to 10 receptor nerve fibers

An outer hair cell shares its innervation with 10 other outer hair cells

Nerve fibers connecting to outer hair cells are both efferent and afferent