Physiology of the Auditory and Vestibular Systems Dr. Pierce

Question 1

Auditory System

Answer 1

Detects sound to locate and identify sound source

Question 2

Sound

Answer 2

Oscillation of air pressure

Question 3

Amplitude

Answer 3

Sound pressure or intensity (dB)

Question 4

Frequency

Answer 4

Number of oscillations or air pressure per second (Hz)

Question 5

High Frequencies

Answer 5

At the base of the membrane structure of cochlea by the oval window

Question 6

Low Frequency

Answer 6

At the Apex of the cochlea (Helicotrema) rather away from the oval window
(Wider and for flexible)

Question 7

The frequency of sound is coded by

Answer 7

Where along the basilar membrane there is the greatest deflection

Question 8

Hair Cells

Answer 8

Polarized epithelial cells with basal side synapsing with nerve and apical cell with actin steriocilia

Question 9

Endolymph is found where

Answer 9

In the Cochlear Duct and Membraneous Labyrinth, Scala Media and produced by Stria Vascularis. Bathes the Apical side of hair cells where the steriocilia is
K+

Low Na+

Question 10

Perilymph is found where

Answer 10

Scala Vestibuli and Scala Tympani, bathes the basal end of hair cells
NA+

Low K+

Question 11

Deflection steriocilia causes

Answer 11

K+ influx

This depolarizes the hair cell which opens the CA+ channels (TRPA1) to increase more positive cations in the cell
NTS (GLUTAMATE) of hair cell is released

Question 12

Hair cell at rest vs active

Answer 12

Hair cell at rest has a slow only continuous APs

When depolarized there is a higher frequency of many APs

Question 13

Steriocilia bend away from biggest one

Answer 13

K+ channels close, hyperlpolarization, Ca+ does not enter since TRPA1 closes

Question 14

Stria Vascularis

Answer 14

Makes Endolymph high in K+ and is highly vascular
= forms Blood-Labyrinth-Barrier where drugs can enter to access the inner hair cells
Some are detrimental due to disrupt the high potential in the endolymph of +80mV

Question 15

Inner hair cells

Answer 15

Primary source of auditory deflection

Which goes to the audition you system

Question 16

Outer Hair Cells

Answer 16

Arranged in 3 rows
Acts as an amplifier front the basilar membrane
Does this by contracting when activated which amplifies the basilar membrane

Question 17

Olivochochlear Efferents

Answer 17

From the Superior Olivary Complex causing the outer hair cells to contract causing the motion in the basilar membrane causing amplification of sound——> through oval window ->tympanic membrane
(Sound that is form the inside)

Branches off the Olivochoclear efferents
Medial Olivary Complex: innervate the outer hair cells
Lateral Olivary Complex: innrevate the inner hair cells

Question 18

Otoacoustic Emissions

Answer 18

Done to infants to test inner and middle ears
These are the sounds made form the olivoacustic efferents and this test listens to make sure emissions are there when they are evoked by pulsing sound in the ear = normal hearing

Can be spontaneous in 1/3 people

From outer hair cells in middle ear constricting

Question 19

Auditory chain STEP 1: Dorsal Cochlear Nuclei and Ventral Cochlear Nuclei

Answer 19

Comes form the cochlea to the Medulla (DCN and VCN)
DCN= integrates acoustic information with the somatosensory information
VCN= processes the temporal and spectral features of the sound (high or low sounds)

BASIC LEVEL PROCESSING

Question 20

Auditory chain STEP 2: Superior Olivary Complex
MSO
LSO

Answer 20

Form the medulla ——-> (GLUTAMATE) excitatory comes to the SON
Info from both ears converge here = TO LOCALIZE SOUND

Medial SON (MSO): generates map of TIME DIFFERENCE between the two ears hearing to find location of the sound

Lateral SON (LSO): generates map of INTENSITY DIFFERENCE between the two ears to find location of the sound

Question 21

Auditory chain STEP 3: Inferior Colliculus

Answer 21

Suppresses echo sounds ,
Which interfere with finding location of sound
adds TIME + INTENSITY difference
=find the final localization of sound

Question 22

Auditory chain STEP 4: The Medial Geniculate Nucleus

Answer 22

Relay station of auditory info to cortex

Many conversions of spectral (intensity) and temporal (time) pathways = allows us to process speech inflections when someone talks

Question 23

Auditory chain STEP 5: Primary Auditory Cortex

Answer 23

IS TONOTOPIC
Conscious perception of sound (begin to interpret sound)
Higher order processing of sound (LOUDness, Modulation of volume, frequency of modulation)

Question 24

TONOTOPIC FEATURES OF PRIMARY AUDITORY CORTEX

Answer 24

More rostral area (anterior)= low frequency -apex of cochlea

More caudal area (posterior)= higher frequency -base of cochlea

Question 25

Auditory (Secondary) Association Cortex

Answer 25

Broca’s and Wernicke’s area More complex sounds responses to music undulations Identify or name sounds, and speech

Question 26

Lateral OC (LOC)

Answer 26

Going to inner hair cells don’t directly go to them

Question 27

Other Olivochoclear Efferents in protecting the ear

Answer 27

=Can freeze the outer hair cells from contracting to dampen the sound and make sure the basilar membrane doesn’t move =Also decreases inner hair cells from responses

Question 28

Middle Ear Efferents in protecting the ear

Answer 28

Motor innervation to the tensor tympani to (malleus, and Tympanic Membrane) and to the Stapedius to (Stapes) = tensing and contracting the muscles to keep the malleus and stapes to not move = work at low frequency to improve hearing them: to help with speech discrimination = work at high frequency: to protect the hair cells

Question 29

Tinnitus

Answer 29

Constant Ringing in the ear | Due to Middle Ear Efferents being damaged

Question 30

Autonomics to protect the ear

Answer 30

Innervation to ear can come from 1. CN 8 2. Caroticotympanic Nerve form the Superiro Cervical Ganglion——> mucus glands of the tympanum and the Ear drum BVs and components 3, Acoustic Nerve (Sympathetic)——> BVs in cochlea Make sure blood in flowing to the parts of the ears, can be maintained of increased by OMM

Question 31

Sensorineural Hearing Loss

Answer 31

Form noise, toxins, age, or unknown Due to Damage to hair cells, or nerve fibers (MOST COMMON FOR OUTER HAIR CELLS, of the BASE of COCHLEA) 1. Damage to outer hair: decreased sensitivity to sound (broader tuning) 2. Damage to the inner hair: to sound input to the CNS Cochlear prosthesis= can restore some hearing

Question 32

Cochlear Prosthesis

Answer 32

An electrode wire is placed through the cochlea and gets stimulated by the frequencies it should stimulate the basilar membrane with and signals surviving hair cells by bypassing damaged areas

Question 33

Anterior Semicircular Canal

Answer 33

Rotation of vertical axis forward | Falling forward

Question 34

Horizontal Semicircular Canal

Answer 34

Rotation on horizontal plane like spinning in circle

Question 35

Posterior Semicircular Canal

Answer 35

Rotation of vertical axes backwards | Falling backwards

Question 36

Utricle

Answer 36

Linear acceleration forwards and back | Running forwards or backwards

Question 37

Saccule

Answer 37

Linear Acceleration up and down | Jumping up to dunk a basketball