Auditory

Question 1

How does the cortex organize information?

Answer 1

It counts action potentials

Question 2

If something doesn’t make it to the cortex…

Answer 2

You don’t perceive it.

Question 3

Receptors for hearing and balance.

Answer 3

Hair cells

Question 4

How do we measure sound?

Answer 4

Intensity= dB
Frequency= Hz

Question 5

What is in the front of the inner ear? What is in the back?

Answer 5

Auditory is in the front. Vestibular is in the back

Question 6

What innervates the tympanic membrane and the ear pinna?

Answer 6

V, VII, IX, and X

Question 7

The stapes sits where?

Answer 7

On the OVAL WINDOW

Question 8

2 main muscles of inner ear and their functions.

Answer 8

TENSOR TYMPANI- adjusts the pressure of the sound and attenuates the level by pulling malleus a little bit away. (Innervated by CN V)

STAPEDIUS MUSCLE- has a quick reflex to pull stapes from oval window when there is an unexpected loud sound. (Innervated by CN VII)

Question 9

The 2 labyrinths of the inner ear

Answer 9

Bony

Membranous

Question 10

What is inside of membranous labyrinth?

Answer 10

High K+ fluid called endolymph

Question 11

What is inside the bony labyrinth?

Answer 11

Perilymph, which is continuous with the fluid surrounding the vestibular system.

Question 12

Best way to stimulate fluid movement

Answer 12

Ossicular conduction

Question 13

What innervates the labyrinths?

Answer 13

Vestibulocochlear nerve fibers (which divide into vestibule and cochlear nerves)

Question 14

What and where is the “hearing structure”?

Answer 14

The cochlea. It is housed in the modiolus.

Question 15

What does the cochlea consist of?

Answer 15

(1) Scala vestibui (oval window)
(2) Helicotrema (apex)
(3) Scala tympani (round window)

Question 16

What are the important structures associated with the cochlear duct?

Answer 16

• It lies between the SCALA VESTIBULI and the SCALA TYMPANI.

- It is separated from them by the Reisner’s membrane above and the Basilar membrane below.

Question 17

Function of basilar membrane

Answer 17

VERY IMPORTANT

We use this because it would be too limiting to use action potentials to directly code for frequency.

Sounds vibrate based on location on basil membrane (high freq is closer to round window, low freq is closer to oval)

Where nerves sit on basil membrane CODES FOR THEIR FREQ.

Question 18

What determines the loudness of a sound?

Answer 18

The amount of Action Potentials

Question 19

Organ of Corti

Answer 19

ORGAN OF CORTI: Sits on Basilar membrane. Is where transduction of pressure waves takes place in the hair cells.

Question 20

Outer vs Inner row of hair cells

Answer 20

OUTER:

• 3 rows
• In V-shaped pattern (increased surface area)
• Displacement sensitive (cells can change their own sensitivity/length based on amount of movement) ONLY ONES THAT CAN CHANGE OWN SENSITIVITY
• Allows for fine-tuning of auditory signals

INNER:

• velocity sensitive
• 99% of hearing comes from this row (this is why outer row functions to adjust freq.)
• not modifiable by CNS

Question 21

The first action potential for the sound occurs…

Answer 21

In the bipolar cells, NOT the hair cells

Question 22

Linkage between hair cells

Answer 22

They are attached via TIP LINKS. Kinocilium are the longest cilium. They are attached to sterocilia. Hair cells are depolarized when the sterocilia bend towards the kinocilium causing the K+ to rush in.

Question 23

What will cause total deafness in an ear? How does this change once you get past cochlear nuclei?

Answer 23

Any injury to the cochlear nuclei or CN VIII will cause ipsilateral (half of hearing, i.e. one ear) deafness.

Past the nuclei there is shared information and hearing is essentially bilateral so you will still have some hearing.

Question 24

Tonotopic map tells us…

Answer 24

Which frequency of sounds go to which parts of the cortex (Heschel’s gyrus)

Question 25

Main 4 nuclei in path of sound to Heschl’s gyrus

Answer 25

(1) Cochlear nuclei
(2) Inferior colliculus
(3) Medial geniculate
(4) Cortex

Question 26

Location of cochlear vs vestibular nuclei in respect to inferior cerebellar peduncle

Answer 26

Cochlear are LATERAL, whereas vestibular are MEDIAL

Question 27

Phase locking

Answer 27

Done by hair cells/ bipolar cells. Allows for temporal resolution. Creates a burst of AP’s at the initiation of a new sound. Cells also hyperpolarize when a sound suddenly ends.

Question 28

Localization of sound

Answer 28

Interpreted by the CNS through 2 methods:

(1) INTERAURAL DIFFERENCE- time between when a sound hits the ear. Whichever ear it hits first while give the direction. (We turn our heads if it’s midline).
(2) PITCH/INTENSITY: When sounds move towards us intensity/pitch increases. They do the opposite when things move away.

Question 29

The main areas/fibers affiliated with language

Answer 29

WERNICKE’S AREA: For comprehension of auditory signals (understanding language)

BROCA’S AREA: Motor and speech

ARCUATE FASCICULUS: Connects Wernicke’s and Broca’s

Question 30

Affect of lesion in Wernicke’s Area

Answer 30

They can talk a lot but it doesn’t make sense. There may be real words but they are nonsensical together.

Question 31

Affect of Lesion in Broca’s area

Answer 31

You can comprehend things but you can’t speak well. You must force each syllable out.