Physiology Of Hearing And Equilibrium

Front 1

sound travels in compression waves through a particular medium

Back 1

vibration of medium

a. solid-----> liquid-----> gas
fastest slowest

Front 2

sound as a wave

series of high pressure areas

Back 2

“compressions”

Front 3

sound as a wave

series of low pressure areas

Back 3

“rarefactions”

Front 4

graphic representation of areas of compression and rarefaction of a sound wave

Back 4

sine wave

Front 5

the distance between 2 areas of compression for a given sound wave

Back 5

wavelength

Front 6

the number of waves that pass a given point in one second (1/s = 1 Hertz)

Back 6

frequency

Front 7

high pitched tones

Back 7

short wavelength/high frequency

Front 8

long wavelength/low frequency

Back 8

low pitched tones

Front 9

20Hz - 20,000 Hz (2-3 Hz distinction)

Back 9

human frequency range

Front 10

intensity of energy in a given wave of sound; signified by height of sine wave

Back 10

amplitude

Front 11

subjective interpretation of the intensity of a sound

Back 11

loudness

Front 12

logarithmic scale to measure the intensity of sound waves

Back 12

decibel

Front 13

0 dB threshold for audibility
10 dB l0 X 0 dB
20 dB 100 X 0 dB
30 dB 1000 X 0 dB
40 dB 10,000 X 0 dB

Back 13

Energy in the Sound Wave

Front 14

barely audible
2 X 0 dB
4 X 0 dB
8 X 0 dB
16 X 0 dB

Back 14

Perceived Loudness

Front 15

human amplitude range

Back 15

0 dB - 120 dB (130 dB = pain level)

Front 16

air -->
external auditory canal -->
tympanic membrane (ear drum) -->
ossicles (malleus, incus, stapes.) -->
oval window of cochlea -->
vibration of cochlear fluid -->
basilar membrane of cochlea

Back 16

Transmission of Sound to the Inner Ear

Front 17

Resonance of Basilar Membrane

Back 17

1.vibration of oval window -> perilymph vibration
2.for 20 - 20,000 Hz only, vibration of vestibular membrane
3.vestibular membrane vibration -> endolymph vibration
4.endolymph vibration -> vibration of basilar membrane
5.basilar membrane “fibers” of different length, thickness, and tension like strings of a
piano

Front 18

different fibers of basilar membrane have different “natural frequencies”

Back 18

resonance

Front 19

vibrate only at SPECIFIC frequency (pitch)

Back 19

SPECIFIC parts of basilar membrane

Front 20

rest on the basilar membrane, contain "stereocilia" which project into
the "tectorial membrane" just above

Back 20

cochlear hair cells

Front 21

a. basilar m. vibration -> hair cell vibration
b. hair cell vibration -> opening/closing channels
c. depolarization/hyperpolar -> cochlear nerve
d. cochlear nerve impulses -> to brain

Back 21

Excitation of Hairs Cells of Organ of Corti

Front 22

cochlear nerve(vestibulocochlear VIII)->
spiral ganglion -->
cochlear nuclei (medulla) -->
superior olivary nucleus -->
lateral lemniscal tract -->
inferior colliculus -->
medial geniculate body of thalamus -->
auditory cortex (superior temporal lobe)

Back 22

Anatomical Pathway to the Brain

Front 23

Processing of Auditory Information

location of vibration on the basilar membrane

Back 23

Perceiving Pitch (Frequency)

Front 24

Processing of Auditory Information

more hair cells of the basilar membrane (with same pitch) are activated

Back 24

Perceiving Differences in Loudness (Intensity)

Front 25

Processing of Auditory Information
localizing Source of Sound

first point where sound from both ears come together

Back 25

superior olivary nucleus

Front 26

Processing of Auditory Information
localizing Source of Sound

the amplitude of sound waves hitting the different ears

Back 26

relative intensity

Front 27

Processing of Auditory Information
localizing Source of Sound

the difference in timing in which a sound reaches both ears

Back 27

relative timing

Front 28

disruption in sound vibrations to basilar membrane (ext & mid ear)

Back 28

conduction deafness

Front 29

conduction deafness

causes

Back 29

1. blocked auditory canal (wax, fluid)
2. perforated tympanic membrane(eardrum)
3. otitis media - middle ear infection / inflammation
4. otosclerosis - hardening of the earbone joints

Front 30

disruption anywhere in pathway from hair cells to the auditory cortex

Back 30

sensorineural deafness

Front 31

sensorineural deafness

causes

Back 31

1. loss of hair cells (explosion, chronic loud noise)
2. damage to vestibulocochlear nerve (VIII)
3. damage to nuclei/tracts to the cortex

Front 32

chronic perception of clicking or ringing

Back 32

tinnitus

Front 33

tinnitus

causes

Back 33

1. sudden blow to the tympanic membrane
2. gradual deterioration of afferents in cochlear nerve

Front 34

effects both hearing and balance; results in tinnitus, vertigo, and
interspersed nausea and vomiting

Back 34

Menierre's Syndrome

Front 35

1. may be too much endolymph beneath basilar membrane
2. symptoms can be treated somewhat with drugs
3. endolymph may be drained periodically
4. hearing loss is progressive

Back 35

Menierre's Syndrome

causes

Front 36

Linear Movement: The Maculae of the Vestibule

bony cavity of the inner ear between the cochlea and the semicircular canals

Back 36

vestibule

Front 37

Linear Movement: The Maculae of the Vestibule

smaller sacs housed within the vestibule

Back 37

saccule and utricle

Front 38

Linear Movement: The Maculae of the Vestibule

patch of "supporting cells" and "hair cells" along the utricles and saccules

Back 38

maculae

Front 39

Linear Movement: The Maculae of the Vestibule

like hair cells of basilar membrane, respond when bent

Back 39

maculae hair cells

Front 40

Linear Movement: The Maculae of the Vestibule

jelly-like sheet that abuts the "stereocilia" of the hair cells

Back 40

otolithic membrane

Front 41

Linear Movement: The Maculae of the Vestibule

"ear stones" that rest on top of the otolithic membrane

Back 41

otoliths

Front 42

maculae of UTRICLE is in the horizontal plane; hairs bend when motion is FORWARD/BACKWARD

Back 42

horizontal acceleration

Front 43

maculae of SACCULE is in the vertical plane; hairs bend when motion is UP/DOWN

Back 43

vertical acceleration

Front 44

three bony "hula-hoop" extensions of vestibule in three different planes

Back 44

semicircular canals

Front 45

like maculae, contain hair cells that respond to flow of endolymph in canals

Back 45

crista ampullaris

Front 46

like otolith membrane, gelatinous "cap" into which hair cells project

Back 46

cupula

Front 47

movement of eyes to remain fixed on object when on "merry-go-round"

Back 47

vestibular nystagmus

Front 48

false feeling of gravity or motion

Back 48

vertigo

Front 49

activated hair cells of crista ampularis ->
afferent axon fibers (vestibulocochlear nerve) ->
vestibular nuclear complex OR cerebellum

Back 49

Equilibrium Pathway: Coordinating Inputs in Brain

Front 50

also receive input from eyes and somatic proprioceptors; coordinates
information to help control motion of eyes, neck, limbs

Back 50

vestibular nuclei

Front 51

also receives input from eyes and somatic proprioceptors; coordinates
information to help regulate head position, posture, and balance

Back 51

cerebellum

Front 52

Problems with Equilibrium

Back 52

1.dizziness, nausea, imbalance, vomiting

2.motion sickness

Front 53

conflict between visual/somatic inputs and action of the vestibular apparatus

Back 53

motion sickness

Front 54

block inputs from vestibular apparatus to the brain

Back 54

Bonine, Dramamine, Scopolamine

Front 55

change in angular (rotational) acceleration

Back 55

movement of the head in non-linear (circular or angular) direction is monitored by three canals