auditory Flashcards
georg von bekesy
we understand how wiring turns into sound perception because of him.
stuck a device in ear while playing sound to see if anything was moving
what is ears structure like
has fluid filled chamber and it vibrates based on frequency
hair tells where vibration is coming from
physics of sound
motion pressure waves in air
what are sound waves
energy transmitted through a physical medium
speed is 340 m/sec or 113 ft/sec (in water-1,500 m/sec)
how to locate prey without vision
send out high frequency, sound bounces back, it vibrates lump of fat in head that acts as a lens
pitch
frequency
loudness
amplitude
timbre
complexity (most sounds are a mixture of frequencies. the mixture determines the sounds timbre or percieved uniqueness)
its like hearing the difference in a trumpet vs guitar
phase
its like when your hands are hitting?
objective vs subjective sound
objective-
amplitude
frequency
complexity
subjective-
loudness
pitch
timbre
loudness is measured in..
decibles (dB)
loudness=
amplitude + frequency
loudest sound ever
kratchu volcano
perception of pitch
varies from person to person because we don’t all have perfect pitch. perceived pitch is a product of complex sound
fourier transform
mathematics of dissecting waves
decomposes a function of time into its constituent frequencies
perceived pitch is determined by..
fundamental frequency
fourier analysis
decodes frequency into complex sounds
know structure of ear
(enter pic here)
pinna
piece of the ear that is cartledge and helps pick up sound
catches sound waves and sends them to rest of ear
outter ear
pinna to ear drum
middle ear
transmits energy from air (thin) to liquid (dense)
protective attenuation reflex
protects inner ear
cochlia
where frequency gets converted to location
has hairs
inner hair
cells carry nerve signal of sound along the auditory to the brain
outer hair
cell receive signals from brain
appear to serve as a mini biomechanial amplifier
focus on particular cells (attention)
loud noises primary damage these hair cells
what happens when inner hair cell bend one direction
they depolarize
the opposite movement with hyperpolarize hair cells
where is tonopopic map located
auditory cortex
how do we “bind together” the inputs from out five senses to perceive an object
we cannot answer this question
human sound vs animal sound
we hear vision more than we hear sound
Pinna
Helps collect sounds from a wide area. More sensitive to sounds coming from ahead than from behind
Plays a part in sounds localization.
Auditory canal
Entrance to internal ear
Tympanic membrane
Eardrum
Moves the ossicles
Ossicles
Smallest bone in body
Transfer movement of tympanic membrane into movements of a second membrane covering a hole in the bone of the skull called oval window
Cochlea
Filled with fluid and contains apparatus for transforming the physical motion of oval window membrane into neuronal responses
Vestibular system
Informs our nervous system where our head and body are moving
What happens when object moves toward patch of air
It compresses the air, increasing the density of the molecules
Outer ear is made of..
Structures from Pinna to tympanic membrane
Middle ear
Tumpanic membrane and ossicles
Inner ear
Apparatus to oval window
What happens once neural response to sound is generated in inner ear
Signal is transferred to and processed by a series of nuclei in the brain stem
then sent to thalamus and medial geniculate nucleus (MGN)
MGN projects to primary auditory cortex
apoptosis
the death of cells which occurs as a normal and controlled part of an organism’s growth or development
what causes a response in sensory neurons for sound?
movement of fluid in the cochlea
what are the steps of out hearing sensation
auditory receptors in cochlea
brain stem (superior olive)
medial geniculate nucleus
primary auditory cortex
mallus->
incus->
stapes->
hammer
anvil
stirrup
eustachian tube and air pressure
pressure is normally the same as outside except for at high altitudes
tympanic membrane bulges at high altitudes
yawning and swallowing opens eustachian tube which equalizes air pressure
what happens when air pressure pushes the tympanic membrane
bottom of mallus is pushed inward and the lever action of the ossicles makes the footplate of the stapes push inward at oval window
why is pressure pushing at the oval window greater than that at the tympanic membrane
surface area of the stapes is smalled than the surface area of the tympanic membrane
attenuation reflux
onset of a loud sound triggers a neural response that causes the tensor tympani and stapedius to contract
this makes chain of ossicles become more ridged and sound conduction to inner ear is greatly diminished
what is the onset of protective attenuation reflex
50-100 ms. this is why sudden loud noises can damage our hearing
purpose of attenuation reflux
adapt to hear continuous sound at high intensities that would otherwise saturate the response of the receptors in the inner ear. this allows us to have a more dynamic range of what we hear
protects us from loud sounds that could damage ear
attenuation reflux and frequencies
suppress low frequencies more than high frequencies. it makes high frequencies easier to hear in a low frewuency environment
parts of inner ear. which have to do with hearing and which do not?
cochlea-hearing
labyrinth-maintains bodies equilibrium
organ of corti
sits upon basular membran and contains auditory receptor neurons
helicotrema
hole in apex of baslar membrane which connects scala vestibuli and scala tympani
fluid in scale tympani and scala vestibular
perilymph. its similar to intracellular fluid and has high Na but low K
fluid in scala media
endolymph- high K but low Na
endocochlear potential
ionic concentration differences in reissners membrane
endolymph is 80mV more positive than that of perilymph
IMPORTANT BECAUSE IT ENHANCES AUDITORY TRANSDUCTION
any motion at oval window must be accompanied by..
complimentary motion at round window. round window bulges out. this is because fluid pressure has nowhere to escape.
ppart of conchlea that is flexible
baslar membrane
response of baslar membrane to sound
movement of endolymph makes baslar membrane bend near its base which starts a wave that propegates to the apex
the distance the wave travels up baslar membrane depends on the frequency of sound
inner hair
has cells that carry nerve signal of sound along the auditory to the brain
outer hair
receives signals from the brain
serves as mini biomechanical amplifier
helps focus on particular sounds
loud noises can damage these hair cells
