Chapter 6.3: AUDITORY Remote Sensing

Question 1

the middle ear bones form a ___ system that converts ____ vibrations into ____ ___

Answer 1

the middle ear bones form a LEVER system that converts AIRBORNE vibrations into PRESSURE WAVES

Question 2

___ ___ from the middle ear travel through the fluid filled ___ in the inner ear that induce vibrations on the ___ membrane

Answer 2

PRESSURE WAVES from the middle ear travel through the fluid filled COCHLEA in the inner ear that induce vibrations on the BASILAR membrane

Question 3

vibrations in the basilar membrane bend the ___ of hair cells on the membrane, depolarizing them, causing them to release ___ onto the axons of neurons in the ___ nerve.

Answer 3

vibrations in the basilar membrane bend the STEREOCILIA of hair cells on the membrane, depolarizing them, causing them to release GLUTAMATE onto the axons of neurons in the AUDITORY nerve.

Question 4

explain the cochlea’s tonotopic map

Answer 4

the tonotopic map allows for sound discrimination.

High frequency sounds excite hairs on the BASE of the cochlea, and low frequency sounds excite hairs on the APEX

Question 5

2 main parameters of sound

Answer 5

1) intensity (dB) aka amplitude of waves

2) frequency (pitch) (Hz)

Question 6

two components of the outer ear

Answer 6

pinna and ear canal

Question 7

the ___ membrane vibrates at the ____ frequency as the sound wave, and separates the outer and middle ear.

Answer 7

the TYMPANIC membrane vibrates at the SAME frequency as the sound wave, and separates the outer and middle ear.

Question 8

three components of the middle ear. How do they work together to convey info the inner ear?

Answer 8

include the malleus incus and stapes. They are all connected by ligaments and vibrate TOGETHER when the tympanic membrane vibrates.

They AMPLIFY sound waves before sending it to the fluid filled inner ear and oval window membrane. Amplification is necessary so the sound waves can move through the fluid.

Question 9

what membrane separates the middle ear and inner ear?

Answer 9

the OVAL WINDOW

Question 10

role of middle ear muscles

Answer 10

they are in the middle ear and contract in response to extremely loud sounds to prevent further amplification and damage to the middle and inner ear

Question 11

the inner ear is comprised of the __ and ___ ___

Answer 11

cochlea and vestibular labrynth.

Question 12

the cochlea is divided into two portions folded onto itself into the scala ___ and scala ____

Answer 12

scala vestibuli and scala tympani

Question 13

scala vestibuli

Answer 13

part of the cochlea that extends from the OVAL WINDOW to the apex of the cochlea

Question 14

scala tympani

Answer 14

part of the cochlea that ectends from the apex to the round window

Question 15

cochlear sound waves travel from the oval window up the ___ and down the ___ toward the round window

Answer 15

up the vestibuli and down the tympani

Question 16

how does the round window allow for sound wave propagation in the cochlea?

Answer 16

if there was no opening, the fluid in the cochlea would not be able to be compressed/moved by the sound waves. The round window essentially provides an opening for the soundwaves to move to.

Question 17

scala ___ lies between the scala vestibui and typanica of the cochlea

Answer 17

scala media

Question 18

the ___ membrane’s width, tension and stiffness DECREASES to the APEX of the cochlea. What does this allow for?

Answer 18

the basilar membrane characteristics changes as it moves from the base to the apex. This allows for the relationship between sound frequency and location of maximal basilar vibration.

Question 19

sound vibrations in the cochlea are sensed by ____ of the hair cells which sit on top of the ___ membrane and project onto the scala ___

Answer 19

sound vibrations in the cochlea are sensed by STEREOCILIA of the hair cells which sit on top of the BASILAR membrane and project onto the scala MEDIA

Question 20

each hair cell has __ stereocilia with dif heights for further differentia

Answer 20

3 rows of stereocilia

Question 21

sounds cause the basilar membrane on the cochlea to vibrate up and down, but the stereocilia vibrate SIDEWAYS. What causes this change in vibrational direction?

Answer 21

the tectorial membrane lies just above the hair cell stereocilia. The outer edge is attached to the basilar membrane where the outer hair cells attach. This causes the basilar membrane to slide sideways against one another.

Question 22

Hair cell’s stereocilia is bathed in ___ that contains large amounts of ___.

Answer 22

bathed in endolymph that contains large amounts of K+

Question 23

Explain hair cell depolarization

Answer 23

the shortest stereocilia contain K+ and Ca2+ channels that open up when the shortest stereocilia bend towards the tallest stereocilia. They are connected together by TIPLINKS. When the sound waves cause vibration of the basilar membrane which cause sideways vibration of the stereocilia, the K+/Ca2+ ion channels in the short stereocilia open, and K+ from the K+-rich endolymph move into the hair cell from the stereocilia channels.

Question 24

How can tip link tension be adjusted? what does this cause?

Answer 24

small myosin motors can adjust tip link tension and alter sound sensitivity. The more tension in a tip link, the larger the vibrations in the cochlea are required to open hair cell ion channels.

Question 25

the K+ and Ca2+ channels on the hair cells are ___ gated

Answer 25

mechano-gated- they open when the stereocilia is physically moved

Question 26

explain how the hair cells in the cochlea release neurotransmitters after depolarization

Answer 26

after mechanogated K+ and Ca2+ channels open promoting initial depolarization, VOLTAGE GATED Ca2+ channels opn and promote further Ca2+ influx.

Vesicle exocytosis of glutamate occurs through the RIBBON SYNAPSE network that is close to the post synaptic cell (SPIRAL GANGLION) which conveys APs into the COCHLEAR NUCLEUS BRAINSTEM REGION

Question 27

Ribbon synapse from hair cells –> ___ ___ —-> ____ nucleus (in brainstem)

Answer 27

Ribbon synapse from hair cells –> SPIRAL GANGLION —-> COCHLEAR nucleus (in brainstem)

Question 28

How is the hair cell in the cochlea repolarized?

Answer 28

opening of K+ permeable channels when the tiplinks pull short stereocilia to the tall stereocilia causes K+ influx into hair cell and flows from the endolymph (causes depolarization and glut release to the spiral ganglion), then K+ moves down into body of hair cell and OUT into the perilymph.

Question 29

stereocilia is bathed in ____, where as the hair cell BODY is bathed in _____. These 2 fluid compartments are separated by cells with ___ ___ between them

Answer 29

stereocilia is bathed in ENDOLYMPH, where as the hair cell BODY is bathed in PERILYMPH. These 2 fluid compartments are separated by cells with TIGHT JUNCTIONS between them

Question 30

Which ions do hair cells use for depolarization?

Answer 30

Ca2+ and K+, not Na+ like neurons.

Question 31

How is the high potassium concentration of the endolymph maintained?

Answer 31

the stria vasciliaris cells that are located on the peripheral wall of the scala media. Has a rich capillary bed and contains ATP pumps to maintain the K+ concentration in the scala media’s endolymph.

Question 32

explain cochlear tonotopy

Answer 32

the higher the frequency of a tone, the closer to the cochlear base will be the hair cells that are most activated by the tone

Question 33

T/F: loudness is also mapped tonotopically on the cochlea

Answer 33

false. loudness is not mapped. varying amplitude of constant pitch (frequency) will be on the same portion of the cochlea.

Question 34

Label lined code

Answer 34

APs in a particular set of axons are interpreted by other neurons according to the label associated with the axon type

ex/ poke yourself in the eye and stimulate the optic nerve. optic nerve fires in response to light. in addition to feeling pain, you will also see stars because your brain think the photoreceptors are firing.

Question 35

benefit of sensory maps

Answer 35

minimizes the connection lengths between neurons encoding similar stimuli.