Power Point 14 Flashcards
________ - frequency is determined by the number of compressed patches of air per unit time that arrive at the ears. Unit: hertz (Hz) = cycles/sec
Pitch
Loudness – intensity – ___________
is the difference in pressure between compressed and rarefied patches of air.
amplitude
The stages of the basic auditory pathway:
Sound wave moves the tympanic membrane.
Tympanic membrane moves the ossicles.
Ossicles move the membrane at the oval window.
Motion at the oval window moves fluid in the cochlea.
Movement of fluid in the cochlea causes a response in sensory neurons.
Three main divisions of the ear:
Outer ear, middle ear, inner ear.
_________ amplify sound pressure onto the oval window.
Ossicles, Ossicles act like levers. Oval window is much smaller than the tympanic membrane.
what two membrane-covered holes at the base:
oval window (contact with ossicles) and round window.
Interior of the cochlea consists of two fluid-filled compartments (termed _______).
scalae, Scala media is the middle compartment. Scala vestibuli and scala tympani are one continuous compartment, however in cross section they appear as two separate chambers.
what pair of elastic membranes separates scala media from the outer compartment
:• Reissner’s membrane • basilar membrane
The basilar membrane is the organ that mediates ______ transduction
auditory
The basilar membrane at the ______ is broader, thinner, and floppier than the ______
apex, base
The membrane is tuned to different frequencies on each point along its length (apex = _____ frequency, base = ________).
lowest, highest
Frequencies are represented along the basilar membrane in a continuous array = _____
tonotopy
The ____________ acts as a mechanical frequency analyzer, separating complex sounds into their constituent frequencies, each analyzed in a distinct physical location.
basilar membrane
The _________ is a thin strip of specialized epithelial cells – the auditory hair cells, and their support cells
organ of Corti
_____________ is a shelf covering the organ of Corti. When the basilar membrane vibrates, shearing motion relative to tectorial membrane causes displacement of the cilia of the auditory hair cells
Tectorial membrane
________ hair cells form a single row
inner
Inner hair cell cilia bundles are pyramidal. The hair bundle extends from the cell’s _______ surface, into the ________. The bundle comprises about 60 cilia arranged in stepped rows of varying length
apical, scala media
Each hair cell is surrounded by supporting cells, forming ________ with its neighbors (like between skin cells)
tight junctions
On the _______ surface inner hair cells receive afferent (about 10 per inner hair cell) and very few efferent synapses
basal
Inner hair cells receive more then ___% of spiral ganglion neurons’ contacts.
95
______ hair cells lie in three rows, farther from the central axis.
outer
On the ______ surface outer hair cells receive very few afferent and robust efferent synapses
basal
Which types of cells do we have more of? inner or outter
outter
_________ of the outer hair cells are equipped with special motors (voltage-sensitive motor protein prestin) that connect to cytoskeleton (actin, spectrin) on the cytoplasmic side of the plasma membrane. This mechanism is unique to the outer hair cells and allows them to extend and contract in response to electrical stimulation.
lateral walls
________ are Tuned to a Particular Frequency and Arranged Tonotopically
Hair Cells
Each hair cell is most sensitive (has the lowest threshold) to stimulation at a particular frequency = _________
best frequency
Best frequencies of adjacent hair cells differ by about ___% (adjacent piano strings are tuned to be about 6% apart)
0.2
The frequency sensitivity of a hair cell may be displayed as a ________
tuning curve
The tuning curve is a graph of a sound intensity required to elicit response in a hair cell at a range of frequencies. It is typically ___-shaped
V
__________________:Direct mechanical gating of K+ channels in the cilia; Electrical tuning allowing for atomic-scale precision in discrimination of sound-wave oscillations, and immediate (no delay) depolarization.
Mechanoelectrical Transduction
_____________: stepwise differences in hair cell cilia lengths and rigidity, and their tonotopic arrangement.
Mechanical tuning
___________: non-linear frequency-specific feed-back amplification in the cochlea due to somatic electromotility of the outer hair cells.
Cochlear amplifier
Unusual ionic concentrations in the endolymph are generated by transport processes in the stria vascularis. These ionic concentrations are responsible for the ________
endocochlear potential
Endolymph:
high K+, low Na+
Perilymph:
low K+, high Na+
Ordinary extracellular fluid, the ________, bathes the basolateral surface of hair cells.
perilymph
A special saline solution, the ________ bathes the cells’ apical site.
endolymph
A bundle of _________ projects from the apical surface.
stereocilia
Stereocilia are Linked by
Tiplinks
_____ influx into the cell from the surrounding endolymph results in depolarization, opening of the voltage-gated calcium channels and the release of neurotransmitter onto spiral ganglion neurites
K+
Enhanced firing =
depolarization
Decreased firing =
hyperpolarization
_________ = continuous firing – modulated by both depolarization and hyperpolarization
Ribbon synapses (glutamate is the principal neurotransmitter)
Inner Auditory Hair Cells are _____________Tuned to Specific Frequencies
Electrical Resonators
The lengths of the hair bundles vary systematically along the _________ axis.
tonotopic
Somatic electromotility:
Outer hair cells are tuned to specific frequencies, arranged tonotopically, and sound-evoked depolarization drives oscillations in the cell’s length.
__________ is the motor protein (expressed in outer, but not in the inner hair cells), that translates depolarization into whole-cell rhythmic oscillations
Prestin
___________:Somatic electromotility of the outer hair cells increases hearing range and discrimination in mammals
Cochlear amplifier
__________ are sounds produced by movements of the basilar membrane in the absence of an external auditory stimulus
Otoacoustic emissions
Efferent fibers robustly innervate outer hair cells, providing feed-back connections that modulate cochlea sensitivity. Principle neurotransmitter – _________
acetylcholine
________ code: Afferent fibers are tonotopically organized.
Place
_________ code: Sound waves oscilations and firing rates are co-linear.
Frequency
Information conveyed by the auditory fibers encodes _______
pitch, volume, and timing
