Audiology I-II-II Flashcards
Sound possesses two primary qualities that are decoded by the auditory system: ______
amplitude (or intensity) and frequency.
The intensity of a sound increases when the air is compressed more forcefully during the peak compression in each cycle, resulting in ____________
increased density of air.
The frequency is the number of times per second that a sound wave reaches the _________. Frequency is measured in Hertz (Hz, cycles/sec).
peak of rarefaction (or compression)
The wavelength of sound (λ), given by: ___________
λ = velocity/frequency.
An audiogram is a graph that shows the audible threshold for standardized frequencies as measured by an audiometer. The Y axis represents ______ and the X axis represents frequency measured in Hertz.
intensity measured in decibels
An audiogram is a graph that shows the audible threshold for standardized frequencies as measured by an audiometer. The Y axis represents intensity measured in decibels and the X axis represents ________
frequency measured in Hertz.
The threshold of hearing is plotted relative to a standardised curve that represents _______-, in dB(HL).
‘normal’ hearing
SPL SOund pressure level
Ratio of pressures relative to a reference pressure
The ___________ is the minimum sound level of a pure tone that an average ear with normal hearing can hear with no other sound present.
absolute threshold of hearing (ATH)
Three parts of the ear
Outer ear
MIddle ear
Inner ear
Pina
“ear” provides 20 decibels
gain
Outer ear
Structure of the middle ear
Stapedius muscle- facial nerve
Tensor Tympani- trigem nerve
Cochlea
is the auditory portion of the inner ear. It is a spiral-shaped cavity in the bony labyrinth
Oval window
a membrane-covered opening which leads from the middle ear to the vestibule of the inner ear.
Round window
sealed by the round window membrane, which vibrates with opposite phase to vibrations entering the inner ear through the oval window. It allows fluid in the cochlea to move, which in turn ensures that hair cells of the basilar membrane will be stimulated and that audition will occur.
Ossicles
three bones in either middle ear that are among the smallest bones in the human body. They serve to transmit sounds from the air to the fluid-filled labyrinth (cochlea).
Conductive vs sensorineural hearing losses
conductive= physical impedance
ex: otitis media
Organ of corti
contains hair cells
Paralymph
like CSF
In the ear (tympani and vestibule)
↑ Na
↓ K
Endolymph
↑K
↓ NA
Scala media
Hair cells
stereocilia (-50 mV resting)- Bathed in endolymph and paralymph
([K] difference)
80 mV electrochemical gradient
3 in outer row (12,000)
1 inner row (3,500)
16,000 total hair cell
Sound energy–> electrical energy
happens in hair cells
The Stereocilia - Tip Links
tension changes K channels–> hyperpolarizes the hair cell
Congenital deafness
colapse of endochoclear potential- stria vasularis- K pump into scala media (mutation in k pump)
Most hearing uses
inner hair cells
acoustic impedance mismatch
Fluid is much more resistant to movement than air; in mechanical terms, water is said to have a high impedance, and air a low impedance. Because of this impedance mismatch, most of the sound’s energy (>99.9%) reaching an air-water interface is reflected back, and and
composed of the pinna and external auditory meatus (ear canal) bounded by the tympanic membrane
external ear
cavity containing the ossicular chain or 3 middle ear bones, malleus, incus and stapes
middle ear
Outter layer hair cells are imbedded in
tectorial membrane (TM)
The _______ is one of two acellular gels in the cochlea of the inner ear, the other being the basilar membrane (BM). located above the sulcus spiralis internus and the spiral organ of Corti and extends along the longitudinal length of the cochlea parallel to the BM
tectorial membrane (TM)
• containing the cochlea and the semicircular canals (part of the vestibular system involved in detection of movement and maintaining balance to be discussed in later lectures)
inner ear
Ototoxic drugs hurt
outer hair cells
sensorineural hearing loss.
occurs from damage to or the loss of hair cells and or nerve fibers. Common causes are 1) excessively loud sounds; 2) exposure to ototoxic drugs (diuretics, aminoglygocide antibiotics, aspirin, cancer therapy drugs); and 3) age (presbycusis).
conductive hearing loss.
When the mechanical transmission of sound energy through the middle ear is degraded
1) filling of the middle ear with fluid during otitis media (i.e., ear infection); 2) otosclerosis, in which arthritic bone growth impedes the movement of the ossicles; 3) malformations of the ear canal (atresia), including “swimmer’s” and “cauliflower” ear; 4) perforation/rupture of the tympanic membrane; 5) interruption of the ossicular chain; 6) static pressure in middle ear. Losses of 10-60 dB can occur in these cases.
Oligochoclear nerve cells
x
Cranial nerve 8 cell types
Type 1= IHC
Type 2= innervate OHC
There are a lot of nerves per IHC
