b/t 150 to 5,000 Hz

intensities are about 30 to 70 dB - the loudest when normally speaking

amplitude correlated with loudness

frequency correlated with pitch

complexity correlated with timbre

how does the sound go into the ear?

• thru the pinna/auricle of outer ear
• thru external auditory canal up to TM
• TM will vib according to characteristics of sound
• TM is attached to a series of 3 ossicles (malleus, incus, and stapes)
• stapes pushes w/in the cochlea
• auditory receptors in the cochlea are activated
• this activation can result in an AP in aud nerve

1. external/outer ear - pinna/auricle, external auditory canal, up to the tympanic membrane
2. middle ear - ossicular chain
3. inner/internal ear - cochlea (auditory system) and vestibular system

pinna/auricle

has different parts:

helix

fossa of helix

antihelix

lobule

etc.

is the eardrum

has:

manibrium

cone of light

quadrant

umbo

etc.

basically composed of the 3 ossicles

malleus

incus

stapes

like a hammer

is attached to the TM (1st in ossicular chain)

has a:

head

neck

handle

2nd in ossicular chain (middle ossicle)

is like an anvil

has different segments

last ossicle in the chain

it's footplate is touching the oval window of the cochlea (footplate pushes back and forth the liquid inside the cochlea)

it's like a stirup

cochlea contains a liquid, a lymphatic liquid, that moves in relation to the vibration/disturbance from the ossicles

furthermore and action potential can be observed in the auditory nerve

function - to protect the ossicles from excessive loudness, they are activating and break the movemtns of the ossiclews to avoid damage

stapedius

tensor tympani

also called stapedius reflex

is an involuntary muscle contraction that occurs in the middle ear of mammals in response to high-intensity sound stimuli

it occurs ONLY at relatively high intensities, activation for quieter sounds can indict ear dysfuntion and absence of acoustic reflex can indicate neural hearing loss

vestibular system - balance and postion of the head

auditory system - related with hearing & represented by the cochlea

semicircular canals

uttricle

sacule

utrricle and sacule together = vestibular sacs

 they are attached to the vestibular nerve

auditory system

cochlea

we can distinguish 3 canals/chambers

1. vestibular canal
2. median canal - organ of Corti found here
3. tympanic canal

has severl turns and coils

in humans, it's about 3 or 3 1/2

in other animials, it is different

in the organ of Corti in the middle canal

they are in b/t the basilar membrane and tectoral membrane in the media membrane

scala vestibuli = vestibular canal

scala media = median cananl

scala tympani = tympanic canal

scala means stair

vestibular duct

cochlear duct

tympanic duct

it is transmitted by different canals

and scala media, we have organ of Corti represented by hair cells

oval window

round window

represented by hair cells that are re-arranged in different ways, in an outer row and an inner row

situated b/t the basillar and tectoral membranes

when liquid is pertubated/moved, then the hair cells/cilia attached to it are also moving or bending

inner hair cells

outer hair cells

high frequency  - will activate mostly areas close to oval window

low frequency - will activate closest to apex or hemicotrema of the cochlea

has 2 branches:

vestibular branch

auditory branch

anterior

posterior

lateral

the liquid inside the semicircular canals also move, hence indicating/informing that the head is moving in a particular directions

goes thru several nuclei:

superior olivary nuclei

inferior coliculus

medial geniculate

primary auditory cortex

crosses over to contralateral side and results in auditory info bilaterally projected so info from right cochlea to right hemisphere and also left hemisphere

so info crossed is more than non-crossed info

(more contralateral than ipsilateral)

cochlea

cochlear nucleus

superior olivary nucleus of the medulla

nucleus of lateral leminiscus in the pons

inferior coliculus in the midbran

medial geniculate body in the thalamus

auditory radiation

auditory cortex

in the upper part of temporal lobe but really towards the insula

Brodman's #3

secondary auditory areas or association auditory areas

association auditory areas in the left hemisphere is known as Wernicke's area

different frequencies projected to different points to the primary auditory cortex

different regions of the basilar membrane project to different areas of cortex

high freq - near base of basilar membrane (oval window)

moderate/low freq - near apex of basilar membrane (hemicotrema of cochlea)

damage is observed in animals that will produce different effects in auditory recognition:

• bilateral damage - animal can detect pitch, intensity difference, but can't detect "tune" (sequencing of sounds)
• inferior coliculus damage - animal cannot detect frequency of intensity differences
• lateral leminiscus damage - animal is deaf

damage in left hemisphere in temporal lobe - results in Wernicke's aphasia (patient can't recognize language)

damage in right hemisphere - then it's auditory agnosia (patient has difficulty in amusia/music, difficulties in recognizing sounds, difficulties in recongnizing voices) - difficulites in recognizing auditory info that is non-related to language

conducitve hearing loss

sensorineural hearing loss

air conduction (usually what we use)

bone conduciton (vibration of bone)

Weber test

Rinne test

tests for lateralization (one sided).

wrap tuning fork strongly on your palm & press the butt of the instrument on the top of the person's head in the midline & ask the patient where they hear sound

normally the sound is heard in ther center of the head or equally in both ears. if there is a conductive hearing loss present, the vibration will be louder on the side of the hearing loss

compares air conduction to bone conduction

wrap the tuning fork firmly on your palm & place the butt on the mastoid eminence firmly. tell the patient to say "now" when they can no longer hear the vibration. when the patient says "now" remove the butt from the mastoid process & place the U of the tuning fork near the ear w/out touching it

again, tell the patient to say "now" when they can't hear if anymore. normally, the patient will have greater air conduction than bone conduction & therefore hear the vibration loner with the fork in the air

if the bone conduction is the same or greater than the air conduction, there is a conductive hearing impairment on that side

if there is sensorineural hearing loss, when he vibration is heard substantially longer than the usual in the air