Audition Flashcards
1
Q
Nature of sound
A
- audible variation in air pressure
- cycle = distance between successive compressed patches of air
- frequency = number of cycles per second = pitch
- expressed in Hz or KHz
- human range = 20-20000Hz
- intensity = amplitude
2
Q
Ultrasound vs Infrasound
A
- unltrasound = greater then 20000Hz
- dogs, bats, fish
- infrasound = lower than 20Hz
- whales, elephants
-predator and prey usually have similar ability to detect sound
3
Q
Movement of sound
A
- Sound waves move tympanic membrane
- Tympanic membrane moves ossicles
- Ossicles move membrane at oval window
- Motion at oval window moves fluid in cochlea
- Movement of fluid in cochlea causes response in sensory neurons
4
Q
Auditory pathway
A
- Auditory receptors in cochlea
- Brain stem neurons (where processing occurs)
- Medial geniculate nucleus (MGN)
- Auditory cortex
5
Q
Attenuation reflex
A
- tympani muscle = anchored to malleus and skull
- stapedius muscle = anchored to stapes and skull
- when muscles contract the ossicles become more rigid and diminish sound
- sound attenuation greater at low frequency than high
6
Q
Structure of inner ear
A
- reisners membrane separates scala vestibuli and scala media
- basilar membrane separates scala media and scala tympani
- organ of corti sits on top of basilar membrane
- contains auditory receptor neurons
- tectorial membrane hangs over
- scala vestibuli + tympani contain perilymph
- scala media contains endolymph
7
Q
Cochlea
A
- base
- closest to round window
- narrow and stiff
- high frequencies
- apex
- furthest from round window
- wide and floppy
- low frequencies
8
Q
Tonotopy
A
-systematic organization of sound frequency within an auditory system
9
Q
Hair cells
A
- auditory receptors that have stereocilia
- sit between basilar membrane and reticular lamina
- rods of corti span both membranes for support
- cells outside rods of corti = outer hair cells
- cells inside rods of corti = inner hair cells
- stereocilia extend above reticular lamina into endolymph
- connected to both membranes
- hair cells form synapses on neurons whose cell bodies are in spinal ganglion
- axons from spinal ganglion enter auditory nerve to project to cochlea nuclei in medulla)
10
Q
Transduction
A
- sound waves cause stereocilia to bend back and forth, so hair cells generate receptor potential that alternately hyperpolarizes and depolarizers
- stereocilia can move from 0.3nm—> 20nm
- inward ionic flow generates hair cell receptor potential
- K+ influx causes depolarization, activating VGCC to trigger release of glutamate to activate spinal ganglion
- majority of auditory info from inner hair cells
11
Q
Cochlear amplifier
A
-outer hair cells act like tiny motors that amplify movement of basilar membrane
12
Q
Audition pathways
A
- afferent from spinal ganglion enter brainstem in auditory-vestibular nerve
- at medulla, axons branches to innervate DORSAL COCHLEAR NUCLEUS + VENTRAL COCHLEAR NUCLEUS ipsilaterally
- axons from ventral cochlear nucleus project to BOTH SUPERIOR OLIVE (bilateral)
- axons then ascend in lateral lemniscus to INFERIOR COLICULUS of midbrain (bilateral)
- ALL ascending pathways CONVERGE in inferior colliculus
- neurons in inferior colliculus project to MGN, then A1
13
Q
Characteristic frequency
A
- frequency at which neuron is most responsive to
- in MGN some cells respond to complex sounds like vocalization and some response to simple selective frequency
14
Q
Intensity coding
A
-encoded by firing rather + number of activated neurons
15
Q
Tonotopy
A
- map of basilar membrane in cochlear nuclei
- not enough to deduce/encode frequency because we need intensity AND frequency
-tonotopy alone above 5khz
