Text 1

Question 1

How sounds is processed

Answer 1

The pressure waves of sound are collected by the pinna and funneled to the tympanic membrane by
the external auditory canal. The tympanic membrane vibrates
in response to the sound, which sets the ossicular chain into motion. The mechanical movement of the ossicular chain then sets
the fl uids of the cochlea in motion, causing the hair cells on the
basilar membrane to be stimulated. These hair cells send neural
impulses through the VIIIth cranial nerve to the auditory brainstem. From the brainstem, networks of neurons act on the neural
stimulation, sending signals to the auditory cortex.

Question 2

Pinna/Auricle

Answer 2

Acts as a funnel and collects and directs sound further into the ear
visible portion of the ear, skin covered cartilage
serves as a resonator, enhancing sound by 4500 Hz

Head shadow effect
– The head may attenuate speech
intensity by 6.4 dB
• Pinna effect
– Each individual's pinna creates a
distinctive imprint on the
acoustic wave traveling into the
auditory canal

Question 3

Function of the outer ear

Answer 3

Collection of sound, localization, resonance and protection

Question 4

Concha

Answer 4

the bowl at the entrance of the external auditory meatus

Question 5

Helix

Answer 5

Upper rim of the ear, The helix has a 2 dB peak at 4000 Hz.

The concha has a 9 dB increase at 5300 Hz.

Question 6

Auricle/pinna

Answer 6

-collects sound waves and

Question 7

ITD (Interaural time distance)

Answer 7

The difference in the two ears sound wave arrival time (pinna/auricle) part of the localization part

Question 8

Ear canal/external auditory meatus

Answer 8

2. 5bcm long, 23-29mm. Outer 1/3 is cartilaginous and contains hair, sebaceous and ceruminous glands. Inner 2/3 is bone and skin. S shaped
   - Resonator: provides about 10 dB of gain to the eardrum at around 3,300Hz
   - Sounds in the 2,000 to 4,000 Hz region are amplified by up to 20db, Noises in this range are the most hazardous to hearing

Question 9

Cerumen

Answer 9

A mixture of skin, sweat, hair, and debris held together with a fluid secreted by glands inside the ear canal.
Purposes: To repel water, trap dust, sand, micro organisms, odor discourages insects, antifungal, moisturizes the epithelium

Question 10

Tympanic membrane

Answer 10

At the end of the ear canal, membranous, cone-shaped, 10mm in diameter. Movements are small about one billionth of a cm.
Made up of 2 sections: Pars flaccid (smaller) and pars tensa (longer)
Vibrates with a magnitude that’s the same as the intensity of the sound wave
Creates a barrier that protects the middle and inner areas from foreign objects
Separates outer and middle ear

Question 11

Muscles of the middle ear

Answer 11

Tensor tympani connects to cranial nerve V - the trigeminal nerve, connected to the malleus

Stapedius muscle - connects to the stapes and cranial nerve V - the facial nerve

Question 12

Function of the middle ear muscles

Answer 12

They help maintain ossicles in proper position, protects the inner ear from excessive sound
levels. When ear is exposed to sound levels above 70 dB, the muscles contract, decreasing amount of
energy transferred to inner ear. This protective reflex is termed “acoustic reflex

Question 13

Middle ear

Answer 13

Air filled space within the temportal bone of the skull and functions as an impedance matching device. Contains the ossicular chain and the eustachian tube

Question 14

Functions of the middle ear

Answer 14

Protects by creating a barrier that protects the middle and inner areas from foreign objects.
Protection from loud sounds.
Conductor: Conducts sound from the outer to the inner ear
Transducer: converts acoustic energy to mechanical energy. Converts mechanical energy to hydraulic energy.
Amplifier: impedance matching of the middle ear.
(only about 1/1000 of the acoustic energy in air would be transmitted to the inner-ear fluids (about 30dB hearing loss)
-Bridge between pressure waves in the tympanic membrane and the fluid waves of the cochlea
Matches the energy transfer from air to fluid

Question 15

Impedance matching of the middle ear

Answer 15

Enhances the transfer of acoustical energy:
1. The area of the eardrum is about 17 times larger than the oval window. The effective pressure is increased by this amount [the force].
2. The ossicles produce a lever action that further amplifies the pressure.
Without the transformer action of the middle ear 1/1000 of acoustic energy in air transmitted to the inner ear meaning 30db loss

Question 16

Eustachian tube

Answer 16

-Connects the front wall of the middle ear with the
nasopharynx.
• Operates like a valve, which opens during
swallowing and yawning
• Equalizes the pressure on either side of the eardrum,
which is necessary for optimal hearing
– Without this function, a difference between the static
pressure in the middle ear and the outside pressure may
develop, causing the eardrum to displace inward or
outward and reduces the efficiency of the middle ear and
less acoustic energy will be transmitted to the inner ear.

Question 17

The inner ear

Answer 17

Sensorineural receptor organ that analyzes sound stimulus
for frequency, intensity and temporal properties
• Transmits information to CNS for further processing and interpretation
Divided into the vestibule, cochlea and semicircular canals
Inner ear is enclosed in bony labyrinth inside is a membranous labryinth of the same shape. The space between membrane and bone is filled with perilymph (scala tympani and scala vestibule) and the inside the membranous labryinth is endolymph (scala media > different fluid composition = electrochemical enviornment

Question 18

Function of the inner ear

Answer 18

Converts mechanical sound
waves to neural impulses
(electrochemical energy)
that can be recognized by
the brain for:
– Hearing
– Balance

Question 19

Perilymph

Answer 19

cochlear fluid high in sodium and calcium

Question 20

Endolymph

Answer 20

Cochlear fluid high in potassium and low in sodium

Question 21

Scala tympani

Answer 21

In the cochlear duct, filled with perilymph, bottom, round window

Question 22

Scala media

Answer 22

middle of the cochlear duct, filled with endolymph
Its the cochlear partition > separates the scala tympani and the scala vestibule
Scala Media has a large positive potential known as
endocochlear potential (EP) and may be the driving force for signal transduction
• +80 mV relative to scala tympani - this voltage difference is called the
endocochlear potential (EP)

Question 23

Scala vestibule

Answer 23

top, terminates basally at oval window, filled with perilymph
Resner’s membrane covers the partition separating it from the scala vestibuli
Basilar membrane base of the partition separating it from the scala tympani

Question 24

Heliotrema

Answer 24

Passage connecting scala vestibuli and scala tympani

Question 25

Vestibular mechanism

Answer 25

Shares inner ear bony labyrinth with the auditory system and the vestibular and auditory nerves form the VIII cranial nerve -provides accurate info about air position in space and about the direction and speed of our movement Consists of 2 groups = otolithic organs (utricle and saccule = linear motion and head positioning) and 3 semicircular canals (rotary motion)

Question 26

The cochlea

Answer 26

``` Sensory organ of hearing Resembles a snail shell and spirals for about 2 3/4 turns around a bony column • Within the cochlea are three canals: – Scala Vestibuli – Scala Tympani – Scala Media ```

Question 27

Organ of Corti

Answer 27

-On the basilar membrane and contains the 2 sensory cells of hearing: Outer and inner hair cells

Question 28

Outer hair cells

Answer 28

elongated or tube shaped, embedded in the tectorial membrane, 3-5 rows of outer hair cells, mostly efferent or motor fibers of the nervous system, receives most efferent fibers from VIII cranial nerve, Stereocilia form letter W There's 12- 13,000 outer hair cells in the cochlea Aid in frequency discrimination • Assist in hearing of soft sounds • May play a role in hearing of loud sounds

Question 29

Inner hair cell

Answer 29

3500 IHCs, One row, Flask-shaped • Receive most afferent 8th nerve fibers •Stereocilia form a line • Stereocilia not attached to Tectorial membrane Rely of OHC for soft sounds • Transmit sound wave information to hearing nerve

Question 30

Stereocilia (cilia)

Answer 30

Approx. a hundred on top of each cell • Three rows of graded lengths • Attached by transverse (lateral) links, both in the same row and from row to row • thin tip links (involved in the mechano-transduction process)

Question 31

Physiology of the Cochlea

Answer 31

Cochlea receives sound wave from ME – Stapes moves annular ligament of the oval window which stimulates sensory cells and causes neural impulses – Perilymph displaced at the basal end of cochlea – Wave propagates toward the apex – Round window moves out of phase with the oval window – Energy converts from mechanical to hydraulic Higher frequencies = closer to the oval window lower frequencies = further from the oval window

Question 32

Basilar membrane

Answer 32

Bottom of the cochlear duct arranged tonotopically, each frequency stimulates a different place The Beskey traveling wave theory Basilar membrane displacement as a function of frequency

Question 33

Beskey's Traveling Wave Theory

Answer 33

Each location of the basilar membrane responds best to a small range of frequencies • The place on the BM with the biggest displacement dictates the frequency response • Frequency responses are arranged from high (base) to low at the (apex= the middle of the cochlear), or tonotopically • Intensity of sound depends on the magnitude of wave displacement or it’s amplitude • The greater is the amplitude of sound wave the larger is the effected area of BM and more nerve fibers fire Traveling wave theory is too simplistic • Describes cochlea as passive • Does not fully explain frequency discrimination ability of cochlea • Bekesy’s observations were made in cadavers • Active mechanisms take part in activation of living cochlea -- Johnstone and Boyle, end of 1990’s

Question 34

Physiology of the Cochlea

Answer 34

Soundwave propagation inside cochlea – Vibration of scala vestibule via perilymph → – Cochlear duct receives the wave due to compressions of Reissner’s membrane → – Endolymph is displaced → – Wave-like motion of the basilar membrane → – Vibrations transmitted to organ of Corti → – Movement of tectorial membrane → – Shearing of hair cells

Question 35

Hair cell transduction

Answer 35

Shearing motion between the hair cells & Tectorial membrane converts sound energy and transmit it to the nerve • Shearing opens up potassium ion channels. The current flowing through these channels alters the cell's membrane potential (this is the electrical response-depolarization): – Resting potential of cell membrane changes to receptor potential (endocochlear potential) • Calcium channels open & calcium ions rush into HC → • Neurotransmitter is released at the basal end of HC • Action potential is elicited & stimulates the nerve endings

Question 36

Auditory Nerve (AN)

Answer 36

AN is a bundle of axons (nerve fibers) that synapse(communicate) with hair cells • Consists of 30,000 neurons • Most fibers connect to IHCs • AN maintains the tonotopic organization of the basilar membrane • Each AN neuron has a characteristic frequency to which it is sensitive

Question 37

From the Auditory nerve to the brain

Answer 37

The auditory nerve sends sound information up through a chain of nuclei in the brainstem • Sound information receives further processing at each nuclei • Final processing occurs in the auditory cortex, located at the top of the temporal lobe in the Sylvian fissure • Additionally, descending neural pathways exist to allow higher centers to control lower centers

Question 38

Ascending Auditory Pathway

Answer 38

Organ of corti to the cochlear nerve to the cochlear nucleus to the superior olivary complex to the lateral lemniscus to the inferior colliculus to the medial geniculate nucleus to the auditory cortex Auditory cortex - organized tonotopically - by frequency Auditory Cortex- Transverse Temporal Gyrus

Question 39

Endocochlear potential

Answer 39

Perilymph has a similar composition to CSF • Rich in sodium (Na) and poor in potassium (K) and calcium (Ca) • Endolymph has a unique composition • Rich in K and poor in Na and almost lacking in Ca • Differences in electrolyte contents of the cochlear fluids create electrochemical potentials • Scala Media has a large positive potential known as endocochlear potential (EP) and may be the driving force for signal transduction • +80 mV relative to scala tympani - this voltage difference is called the endocochlear potential (EP)

Question 40

Audiologist

Answer 40

An audiologist is a healthcare professional conceerned with the assessment, rehabilitation and habilitation of hearing and balance disorders

Question 41

The role of an audiologist

Answer 41

Diagnostician, therapist, dispenser, consultant and researcher

Question 42

Hearing loss in the US statistics

Answer 42

1 in 8 people over the age of 12, 13%, 30 million have hearing loss in both years 2 out of 3 children were born with a detectable level of hearing loss in 1 or both ears

Question 43

The father of audiology

Answer 43

Dr. Raymond Carhart

Question 44

Sound

Answer 44

vibratory energy transmitted by pressure waves in the air or other media

Question 45

Hearing

Answer 45

The preception of sound

Question 46

Where does sound come from?

Answer 46

The compression of molecules in the medium through which it's traveling Air is a sound medium

Question 47

Requirements for sound:

Answer 47

- There must be a source of vibrational energy - The energy has to then be delivered to and cause a disturbance in the medium - Medium needs to have mass and be compressible or elastic - The disturbance is spread in the form of sound waves and they form a compression of a medium or condensation and expansion of the medium or rarefraction

Question 48

Condensation

Answer 48

Density of air moleules are increased, causing increased pressure

Question 49

Rarefraction

Answer 49

density of air molecules decrease, causing decreased pressure

Question 50

Simple Harmonic Motion (sinusoidal motion)

Answer 50

The back and forth movement of an object

Question 51

Cycle

Answer 51

One complete period of compression and rarefraction of a sound wave

Question 52

Phase

Answer 52

Any stage of a cycle

Question 53

Intensity

Answer 53

the magnitude of a sound = loudness or the distance a molecule moves

Question 54

Audiogram

Answer 54

A graph of thresholds of hearing sensitivity as a function of frequency

Question 55

Frequency

Answer 55

The number of cycles occured at 1 speed, the speed of vibration

Question 56

Pitch

Answer 56

the perception of speech

Question 57

Displacement

Answer 57

The movement of a molecule

Question 58

A period

Answer 58

The length of time for a sine wave to complete a cycle

Question 59

Sinusoid

Answer 59

A periodic wave that repeats itself at regular intervals ata time

Question 60

Spectrum

Answer 60

Different frequencies in sounds , complex sounds

Question 61

Blood supply to the auditory nervous system

Answer 61

2 sources: One that supplies the brainstem structures (basiliar artery) and the other supplies cortical structures (middle cerebral artery)

Question 62

Processing of speech info

Answer 62

occurs throughout the central auditory system

Question 63

The left temporal lobe

Answer 63

Primary location for processing information The right EAR is dominant for processing info too

Question 64

dynamic range

Answer 64

the range between the threshold of sensitivity and the treshold of discomfort