physiology of hearing-1

pats of auditory physiology

outer ear function

middle ear function

inner ear function

- vestibular mechanism

- auditory mechanism

>>>>mechanical energy

>>>>electrical energy

auditory pathways in the brain

conversational pitch as at ____________

1500-4000 Hz

shape of the pinna and EAM determines ____

which sounds are enhanced; how high or low frequency is

other ear function

pinna: collector go sound or a sound funnel

EAM: funnels sound to tympanic membrane

both selectively enhance certain sounds between 1500 Hz and 8000 Hz

the _______ is humans is especially good in collecting sound from the side or front

pinna

you can hear in the range __________ Hz

20-20000 Hz

__________ is the different frequencies of soundless amplified or dampened according to the shape of the tube they're in; deciding which frequencies to be (louder or quieter)

resonance

why does sound get louder at the stapes?

vibrations are harder to create in fluid than in air, so intensity needs to increase so that vibration is carried through

middle ear is ___________ while the inner ear is ________

air-filled; fluid-filled

pressure=

force/area

to increase pressure, we must increase ________ or decrease _________

force; area

sound is measured in __________

pressure

dB

2 big things in sound: __________ and ________

frequency (pitch)

intensity (dB)

tympanic membrane area

55mm^2

oval window area

3.2 mm^2

can't really increase force, but can change area...

decrease area between tympanic membrane and oval window so that pressure increases and vibration continues throughout the ear

____________ is resistance to the flow of energy

impedance

does fluid or air have more impedance?

fluid

impedance analogy

mom yelling at kid who is underwater; few sound waves got through the water

most bounce off--like the middle ear to the inner ear!

# of impedance-matching functions

2

impedance matching function #1

the ratio of the tympanic membrane area to that of the oval window is 17:1. this difference produces an increase of about 2.5 dB

makes sound more intense

area is decreasing so pressure is increasing

the more intense a sound is, the ______ it is

louder

impedance-matching function #2

the length of the manubrium is about 9 mm, that of the stapes is about 7 mm--> this difference in the two "levers" produces a gain of about 2 dB

bigger to smaller area, pressure increases

total gain in impedance-matching functions is ________

27 dB

_________ is the inflammation of the middle ear

otitis media

_________ is the ossification of the middle ear bones, especially the stapes

otosclerosis

otosclerosis in men v women

2x common in women

inner ear functions

vestibular mechanism

auditory mechanism

frequency, intensity, and sound placement is determined by the ______ to determine sounds

brain

auditory mechanism

the inner ear is responsible for performing spectral and temporal acoustic analyses of the incoming acoustical signal (sound waves coming in)

temporal acoustic analysis

ear has to get sounds in right order (and brain needs to interpret in right order)

______________ is the process of extracting defining the various frequency and intensity components of a given signal

spectral analysis

fricatives (hissy) have ________ frequencies, vowels have __________ frequencies

very high; low

high v low frequency hearing loss

high: can't hear fricatives

low: can't hear vowels

______ is a motor programming deficit

apraxia

spectrogram

a graphic representation of the three major parameters that describe the acoustic characteristic of any sound: time, frequency, and intensity

parts of acoustic mechanism

1. mechanical transmission

2. electrical transmission of auditory signal

mechanical transmission (pt 1)

transmission of sound waves from air to fluid

sound waves moving in and out of fluid-filled--motion/waves created

motion goes to basilar membrane and moves it up and down

movement especially in perilymph

mechanical transmission (pt 2)

vibration of oval window creates standing/traveling wave

wave got tot the membrane and makes the membrane move up and down more

because of the frequency of sound, different parts of the wave will react (sorting out sound by frequency starts here)

mechanical transmission (traveling wave; pt 3)

deciphering sounds begins here!

high frequency sounds--> processed at basilar membrane at basal end of cochlea

low frequency sounds--> basilar membrane at apex of cochlea

mechanical transmission (pt 4)

basilar membrane moves up and down because of waves

cilia of the outer hair cells are embedded within the tectorial membrane; they move because the tectorial membrane moves

shearing action

if basilar membrane moves up and down, organ of court will move up and down

little hair cells start bending (inner hair cells transmit sound, outer hair cells are cochlear amplifiers)

inner hair cells are thought to be moved just by the movement of the endolymph

cochlear amplifiers

outer hair cells

make cochlea more sensitive; make sound louder or more intense

electrical transmission of auditory signals (pt 1)

the bending of the stereocilia causes changes within the hair cells that create electrical signals (electrical potentials like action potentials)--> the auditory nerve fibers are below the hair cells and they pass these signals on to the brain

electrical transmission of auditory signals (pt 2)

the movement of a hair cell's cilia bundle opens ion channels at the tops of the cilia

at inner hair cells, sound, motion energy move stereocilia

gates open (Na+, K+, C++ mvmt)--electrochemical

stereocilia are connected by __________

tip-links

tip-link action

bend the hair cells to open the gates and allow movement of ions

Na+ ions are located in _______

perilymph

K+ ions are located in __________

endolymph

C++ moves...

when calcium hits glutamate, it's released and information goes to the cochlear nerve

95% of nerve fibers go to __________

inner hair cells

inner hair cels carry sound itself