Hearing Flashcards
What are the parts of the outer ear
pinna, external auditory meatus (aka ear canal)
What are the parts of the middle ear
tympanic membrane, ossicles, eustachian tube
What is the order of the ossicles
malleus, incus, stapes
What are the parts of the inner ear
vestibular and cochlea
What are the 3 sections of the cochlea
scala vestibuli, scala media (cochlear duct), scala tympani
Sound waves are characterized by…
frequency and intensity (pitch and loudness)
The oval window and the round window…
separate the fluid-filled inner ear from the air-filled middle ear
the steps of sound transmission
the ear cannal collects the sound waves, the sound waves vibrate the tympanic membrane which moves the ossicles, the stapes foot plate moves in and out of the oval window sending the vibrations to the cochlea, when sound energy is transferred to the cochlea the basilar membrane vibrates up and down causing the outer hair cell sterocilia to shear on the tecorial membrane above, this shearing action causes the stereocilia to bend which opens ion gates and leads to chemical changes (nerve impulse travels to auditory nerve)
__________ initates the tympanic reflex
loud sounds
tympanic reflex
tensor tympani and stapedius muscles contract; sound transmission decreases (protective= prevents strong sound waves from causing excessive stimulation of the auditory receptors)
round window
where sound waves exit the cochlea
As sound wave move the fluids in the cochlea…
the basilar membrane vibrates and the stereocilia of the hair cells are bended
When the inner hair cell is bent toward the tallest stereocilium, it is
depolarized (influx of K-> opens Ca channels -> vesicle release of neurotransmitters)
when the inner hair cell is bent away from the tallest stereocilium it is
hyperpolarized ( no K influx-> no activation of calcium channels (no calcium influx)-> no positive ions in cell)
hair cells are in what kind of ionic environment
endolymph: high potassium (outside), low sodium
Inner Hair Cells
primary sensory receptors
Outer Hair Cells
shorten when depolarized, increase the amplitude and clarity of sound
How are different tones coded by the cochlea?
by different regions of the cochlea
What part of the cochlea responses to low pitch?
near distal end
What part of the cochlea responses to high pitch
near the round window
Detection of the frequency of a sound above 5kHz is based on
the location along the cochlea of the most intensely stimulated hair cells
For a frequency below 2000 Hz how is frequency detected
both firing pattern of CN8 and the region of hair cell activation can give the brain ideas about the pitch
The frequency of the action potential is proportional to
the loudness of the sound
Major Auditory Pathways (in order)
cochlear ganglia-> dorsal and vental cochlear nuclei ->superior olive -> inferior colliculi -> medial geniculate body (thalamus) -> primary auditory cortex
dorsal and ventral cochlear nuclei
2nd order neurons respond from 1 ear (same side)
superior olive
respond from both ears (where info crosses)
inferior colliculi
centers of auditory reflexes
primary auditory cortex
tonotropic, very plastic
Superior Olive
sound localization: loudness difference (important for freq about 3000 Hz); detectable time difference (most important for frequencies below 3000 Hz)
Conductive deafness
impared sound transmission external or middle ear; impairs all sound frequencies
Sensorineural deafness
transmission of nerve impulses is impaired: loss of hair cells; impairs ability to hear some pitches more than others
function of the pinna
protection; helps detect where sounds are coming from
sound waves vibrate the eardrum which vibrates the 1, 2, 3. The foot plate moves in and out of the 4 and transfers energy to the 5
malleus, incus, stapes, oval window, endolymph cochlea
Along the basilar membrane there are 2 types of sensory cells:
the outer and inner hair cells
How are hair cells arranged
by the frequency they detect
Where is the organ of corti located
cochlear duct or the scala media
The ________ is filled with a fluid with an abnormally high K+
cochlear duct or the scala media
