Special Senses 1 Flashcards
What is the equation for the speed of sound?
m/sec = (wavelength)*(frequency)
High frequency sound has short or long wavelength?
short
[m/sec = (wavelength)*(frequency)]
What determines the intensity of sound?
The amplitude
What is the basis for sound?
Movement of air molecules
True of false: loudness can be measured by machines?
False–only amplitude
What does loudness depend on?
Both frequency and sound pressure
What is the equation for sound level pressure (dB)?
20log(P/Pr): P=sound pressure, Pr=reference pressure
What is the range of human hearing (in Hz)?
20 Hz to 20,000 Hz
What is the range of frequencies over which we hear best?
1-4 kHz
What can cause a notching an audiogram?
Killing hair cells = loss of hearing range
What are the two factors that can determine hearing loss?
How loud
How long
What is the purpose of the pinna?
Localizing sound in the vertical plane
The external auditory meatus has a resonant frequency of what? What is the purpose of this?
3,500 Hz–this increases sound pressure at the TM
What is the purpose of the Eustachian tube?
Equalize pressure in the middle ear with outside environment
What is the main function of the ossicular system?
Provides impedance match between outer and inner ear
What are the two muscles in the middle ear, and what is their innervation?
Stapedius – CN VII
Tensor tympani– CN V
Which is window that receive input from the stapes: the oval or the round? What is the other used for?
Oval
Round is for pressure balance
What is the sensory input to the middle ear attenuation reflex?
CN VIII
What is the motor output of the attenuation reflex?
CN VII to stap
CN V to tensor TM
What is the effect of Bell’s palsy on the attenuation reflex?
Loss of CN VII efferent to stapedius causing hyperacusis
Is Bell’s palsy a LMN or UMN problem?
LMN of CN VII
What is the treatment for Bell’s palsy?
Steroids to prevent swelling from CN VII
When do the middle ear muscles (stapedius and tensor tympani) contract regularly?
During speaking
What is the small coiled structure in the ear that contains the organ of Corti?
Cochlea
What is endolymph? What ion is found in high concentration here?
Fluid in the cochlea
K
What is perilymph? What ion is found in high concentration here?
Fluid in scala vestibuli and scala tympani
Na high, (K low)
What are the spaces found around the scala media? (above and below)
Above = scala vestibuli Below = Scala tympani
What is the fluid the contacts the top of the hair cells? Bottom?
Top = endolymph Bottom = perilymph
What is the structure that produces endolymph in the scala media?
Stria vascularis
What is the effect of some diuretics on the ear?
Damage the stria vascularis
Failure of what cells to move into the ear can cause hearing loss?
Melanocytes
What is the layer of fluid that lies over the hair cells?
Tectorial membrane
What are the hair cell names that sit below the tectorial membrane?
Stereocilia
How many afferent nerves are there per hair cell?
One afferent fiber innervates just one hair cell but several fibers might synapse with one hair cell.
What is the function of the inner hair cells?
Actual sensory receptor
What is the purpose of the high [K] in the scala media endolymph?
Allows for ion gradient so flow into the hair cells
Why does a hereditary problem with gap junctions cause hearing loss?
Loss of feedback of K+ from the hair cells to the stria vascularis
What is the function of the outer hair cells?
Contract and expand the tectorial to sharpen frequency resolving power
What is the origin of the olivocochlear bundle?
Superior olivary nucleus
What is the helicotrema?
End of the cochlea where sound waves turn around
What is the relationship between increasing Hz and the distance from the stapes?
Higher Hz means peak the most movement of the basilar membrane occur at lower distance
What is the tonotopic map?
Different points along the cochlea are used to detect different frequency sounds
High frequencies occur where in the cochlea?
Early–near the stapes
Low frequencies occur where in the cochlea?
Near apex of the cochlea
Where in the brainstem is the CN VIII nucleus?
Posterior medulla
What structure in the pons does the cochlear fibers go (some cross over) to?
Superior olive
Where do fibers from the cochlear nucleus go after they (cross over) in the pons at the superior olive? (3)
Lateral lemniscus, then inferior colliculus, then medial geniculate complex
Does frequency map in the auditory cortex
Yes
How are sounds localized?
auditory neurons compare loudness of sound arriving in each ear, or the arrival of the sound
What is the structure in the brainstem responsible for the reflex of the eyes and hearing?
Colliculus
What is the structure in the brainstem that is utilized in localizing sound?
Superior olive
What is the cause of conductive deafness?
impaired sound transmission in the external or middle ear
What is otosclerosis?
Genetic disease where bone is deposited around the stapes
True or false: OM with effusion can cause conductive hearing loss
True
What is the problem with conductive hearing loss early in life?
Inability to distinguish between sounds hinders language development
What is the disease associated with vestibular Schwanomas (acoustic neuromas)
NFM II
What is Meniere’s syndrome?
Overproduction of endolymph
What is the cause of central hearing loss?
Lesions to central auditory nuclei and pathways
Why is it that unilateral damage to ascending auditory pathways has only subtle effects on hearing?
So much crossing
What is the disease that can cause defective sound localization?
MS
True or false: humans emit tones from their ears
True
What is the clinical application of otoacoustic emissions?
screening tool since patients with sensory hearing losses of greater than 30 dB do not usually have these emissions.
