Hearing Flashcards
what is the functional component of the hearing system?
SSA
what is frequency?
the pitch of a sound
higher freq= consonants and tremble
lower freq= vowels and bass
need more or
what is normal frequency?
20-20,00 Hz
most effective at 2-4 kHz
what is normal voice range?
500 Hz to 2 kHz
what is loudness?
a function of amplitude= volume
expressed as dB
human= 1-120 dB
>100 = damage >120= you can't hear
need more or less amplitude based on the volume
what are the anatomical structures of the external ear?
pinna (auricle) acts as a funnel, channeling the airbo
auditory canal= 2.5 cm
what are the functions of the middle ear?
converts sound waves in air into waves in a fluid
what are the anatomical structures of the middle ear?
tympanic membrane- conical in shape- point extends into the cavity
ossicles- sound amplification
what constitutes the ossicles?
malleus- hammer- connects rigid with..
incus- anvil- connects flexible with..
stapes- stirrup- flat bottom (footplate) moves in and out like a piston
what are the 2 ways bones amplify air waves?
1- force
2- surface area
tympanic membrane is much larger than the membrane of the oval window
the lever system of the ossicles increases the mechanical advantage
what are the 2 muscles associated with the middle ear?
tensor tympani- inserts into malleus
stapedius
the 2 contract to decrease the sound (modulation) (dampen piston action when contracted)- helps prevent ear damage from loud sounds
increase/decrease amplitude
what is the function of the tensor tympani?
what is it innervated by?
functions: decrease the amount of movement of the ear drum
innervated by CN 5
what is the function of the stapedius?
what is it innervated by?
functions: restricts the movement of the footplate of the stapes against the oval window
innervated by CN 7
what is the anatomy of the cochlea?
spiral shaped canal- makes 2.5 turns and 32 mm long, 2 mm diameter
cochlear partition divides the bony labyrinth into:
- scala vestibuli
- scala tympani
- the partition contains the cochlear duct (scala media)
the cochlear partition has 2 membranes:
-vestibular membrane (reissners membrane)
-basilar membrane
These 2 membranes separate the endolympth filled cochlear duct from the perilymph filled scala vestibuli and tympani
helicotrema= apex of the duct (end)
what is the anatomy of the basilar membrane?
wider at the apex by a factor of 5
membrane tension is > at the base & decreases to apex (base 100x stiffer)
- High freq= stiffer, base will vibrate dissipating most of energy and the wave will not propagate far
- Low freq= generate waves that travel all the way to the apex before energy dissipates
sound waves cause movements of the cochlear portion including the basilar membrane. these movements of the basilar membrane stimulate hair cells of the organ of Corti
what is the organ of corti?
runs longitudinally along the entire length of the basilar membrane
acts as a transducer
hair cells are sandwiched between the basilar membrane and a thin sheet of tissue called the Reticular Lamina (hold onto hair cells)
hairs go through and extend into gel substance of the tectorial membrane
wave moves basilar membrane- the entire foundation holding hair cells moves and therefore cells and membrane move as a unit, pivoting up to the tectorial membrane or away from it
bending hair cells= increase K = depolarization
what are the 2 types of hair cells?
inner- hear
outer- can alter their length
- 3 outer to 1 inner
- <5% of spiral ganglion cells communicate with them
- ROLE IN MODULATING ORGAN OF CORGI- selection of attention
how does the size of the basilar membrane differ from its base to the apex?
wider and floppy at the apex- low frequencies
narrow and stiff at the base- high frequencies
what is the tonotypical arrangement of the cochlear nuclei?
high frequency- dorsal
low frequency- ventral
> 4 parallel ascending pathways
what is inter aural time delay?
the time the sound reaches each ear
figured by the peak in the waves used
good for low frequency sound
high frequency- 1 cycle of sound is smaller than distance between ears, therefore doesn’t work well
if sound is in front or back of your- no delay
90 degrees sound- the sound wave will hit one ear faster than the other - helps determine direction of sound
what is interaural intensity differences?
head casts a shadow from the high frequency
low frequency diffracts sound around the head, thus no shadow
sound from side, hits ear directly. head causes shadow so other ear hears it a little less (blocks sound, doesn’t go around) high freq only
no way for a vertical sound
how does the pinna shape affect sound?
bumps and ridges of the outer ear produce reflections of entering sounds
the delays between direct and indirect paths cause sound delays
hit at different intensities
auditory reflexes:
olivocochlear efferents:
- selective tuning
- focusing
- ?protection
somatic motor:
- load sounds- contraction of ear ms
- startle responses- tectospinal tracts
what is conduction deafness?
results from any interference with the passage of sound waves through the external or middle ears
never complete or total
what is nerve deafness?
results from damage to the receptor cells of the spiral organ or to the cochlear nerve
common to both air and bone conduction
hearing loss therefore occurs in both routes
hearing loss related to the amount of damage
what is the weber’s test?
256 (512) Hz tuning fork
place on midline of head & ask what patient hears
normal = hears equally in both ears
Conduction deafness = sound seems louder (localizes) in decreased hearing ear
Nerve Deafness = sound seems louder in unaffected ear (localizes) (ear more sensitive)
what is Rinne’s test?
compares hearing via air and bone conduction
256 Hz tuning fork
Place tuning fork on mastoid process
then place it near ear and hold until it can’t be heard
Normal = sound is heard louder and longer by air conduction
