inner ear Flashcards
Be able to label the parts of the organ of corti
Look on google doc notes
What are the characteristics of IHC
stereocilia in U pattern
1 row
What are the characteristics of OHC
stereocilia in V or W pattern
3 rows
*they can emit their own sound because they have a feature called motility
What is motility
existing or capable of movement (the ability to move spontaneously and actively)
What is the primary role of the mechanical response of the inner ear
convert mechanical vibrations at the stapes and of the inner ear fluids into neural (electrical) responses in the auditory nerve
How is the motion of the basilar membrane described
as a paradoxical traveling wave
Why is the basilar membrane paradoxical
if you stimulate the apical end, the basal end will move first
Basilar membrane is organized so that it is represented by independent oscillators
Even if you damage one place it can still function
Stiffness gradient works across the entire length of the basilar membrane to enable tonotopic organization
What is the evidence that the basilar membrane is not stretched
paradoxical traveling waves
if you cut the BM it does not stretch
What are the two types of otoacoustic emissions
spontaneous
evoke
What are otoacoustic emissions evidence of
evidence that the basilar membrane is nonlinear
In what percent of ears do spontaneous emissions occur
50%
What are transient evoked otoacoustic emissions
present a short duration sound in the ear canal of a person
sound sets the outer hair cells into oscillation
can record the echo in the ear canal
What are distortion produce otoacoustic emissions
present subject with 2 primary tones: f1 and f2
f2/f1 = the biggest cubic distortion product
measure energy at 2f1-f2 to record the emission
if its audible its a combination tone
f2-f1 = simple difference tone
What are cochlear voltages
a voltage in the inner ear
What is an alternating current
can either be cochlear microphonic (mimics the stimulus) or action potential
in both cases the stimulus is induced
What is direct current
can either be resting potentials or summating potentials
summating potentials have stimulus induced and are helpful in diagnosing meneire’s disease
What is resting potential and what are the two types
voltages that are present in the cochlea in the absence of sound
endocochlear potential: an extracellular potential that you can record in the endolymph
hair cell potential: an intracellular potential
What is the total voltage gradient between the EP and the hair cell potential
160 mV
anything that we hear has to be represented through what?
the firing of the 8th auditory nerve
What are afferent fibers
(what are the two types)
carry information up to the central auditory system
radial fibers: comprise 85-95% of the total number
- innervate only inner hair cells
- 20:1 ICH ratio, many to 1
- primarily responsible for carrying information about sound to the brain
outer spiral fibers: comprise 5-15% of fibers
- innervate only the outer hair cells
- unmyelinated, skinny, slowly conducting
- 1:10 OHC ratio, 1 to many)
unknown function
what are efferent fibers
carry information back down from the central auditory system
What’s on the vertical and horizontal axes of a neural rate intensity function
x axis = intensity (dB SPL)
y axis = firing rate (spikes/sec)
when no sound is presented, what will the neuron fire at
its spontaneous rate
What kind of relationship do Spontaneous rate and threshold have
inverse
