PSYC 2200 EXAM #3 STUDY GUIDE
The inner ear - Answers - -cochlea
-basilar membrane
-organ of corti
-cells
cochlea - Answers - spiral structure made up of 3 fluid-filled tubes wound around a
cone-shape bony core; mission is mechanical amplification of sound
basilar membrane - Answers - runs along length of cochlea; exposed to the fluid waves
triggered by the vibrations of the oval window
-->Fluid vibrations of different frequencies will cause different parts of the basilar
membrane to vibrate, effectively creating a tonotopic map of the incoming frequencies
♣ Small, tight basal end vibrates in response to higher frequency vibrations
♣ Large, floppier apical end vibrates in response to lower frequencies
sounds appear as - Answers - a traveling wave down the basilar membrane
difference in vibrations between tympanic membrane and basilar membrane causes -
Answers - sheer force of hair cells
hair cells transduce information - Answers - act as receptors
Inner hair cells - Answers - code frequencies
-Transduce sound into electrical signals that will be interpreted by the CNS
-limited #, once gone they are gone
-Mechanoelectrical transduction: Motion of hair bundles causes slide relative to each
other tension on tip links pulls open ion channels at ends of links ultra-rapid
depolarization of the cell release of neurotransmitters at the other end of cell
-Opening channels depolarizes cell, closing channels hyperpolarizes cells
organ of corti - Answers - -lies on top of basilar membrane; sharpens sound frequencies
-Packed with 3 rows of outer hair cells (run parallel to inner hair cells)
outer hair cells - Answers - Amplifiers
-Cell's bottoms are lodged in the basilar membrane and their hair bundles are
connected to the overlying tectorial membrane
-In response to oscillating voltage, they physically shorten and lengthen, cycle for cycle,
as fast as the sound itself
-Transduction is mediated by special proteins in the outer hair cell membrane
,-Location allows them to mechanically amplify the incoming sound, making it much
more detectable and sharply tuned --> inner hair cells then receive a much better signal
most frequencies are coded by the - Answers - Place theory or labeled line
-depends on traveling waves
-output of any receptor is clear & tells you exactly what is going on
-cochlea acts as frequency analyzer
-Different neurons carry different, specific information
-The frequency of a stimulus is encoded by the set of afferent fibers that happen to
innervate the hair cells stimulated by that frequency
-Fibers carry information that is "labeled" with a given frequency
-Labeled lines are also used in sensory, visual, vestibular, and somatosensory systems
characteristic frequency - Answers - for a given frequency of sound, only inner hair cells
along distinct portions of the basilar membrane will be stimulated
Spatial separation of vibration frequency breaks down complex sounds into their
component frequencies - Answers - The brain receives all of the individual frequency
components of the sound
8th cranial nerve - Answers - auditory vestibular nerve
-sends information to cochlear nuclei
-"cochlear nerve"; consists of the fibers connecting the cochlear inner hair cells to the
cochlear nuclei in the brainstem
Afferent fiber: neuron transmits signals from the cochlea to the brainstem - Answers -
Each afferent neuron innervates a single hair cell, although each hair cell may be
contacted by 20 or more afferent fibers
tonotopic map - Answers - information in cochlear nucleus is arranged in this way
-organized based on frequencies
-each afferent fiber is activated only by signals of a particular frequency
auditory pathway - Answers - outer ear --> middle ear --> cochlea --> auditory nerve -->
cochlear nuclei (in brainstem) --> olivary nuclei on both sides of the brainstem -->
passes over the lateral lemnisci to the inferior colliculi --> medial geniculate nucleus (of
the thalamus) --> primary auditory cortex (A1)
Primary auditory cortex (A1) - Answers - -in the temporal lobes of the brain
-Tonotopic map
conduction deafness - Answers - Deafness can result from damage to the outer or
middle ear that prevents transmission of sound information to the cochlea
,Sensorineural deafness - Answers - deafness due to damage to the cochlea itself,
usually involves the hair cells
When there is no damage to downstream auditory pathway - Answers - patients can
"hear" useful representations of sounds that they can train their brains to interpret
o Hearing aids: amplify sounds so that impaired structures can perceive and transmit
them
o Cochlear implants: completely bypass patient's nonfunctioning cochlea and transmit
sounds directly to auditory nerve
Damage that affects auditory system downstream of inner ear usually does not result in
deafness - Answers - but rather in deficits in the ability to process sounds
o Damage to A1 on one side of brain (unilateral damage) --> impaired sound
localization
o Damage to higher areas (A1 and A2) --> inability to interpret sound
A1 is responsive only to basic sounds and their modulation - Answers - higher areas of
auditory cortex make it possible to understand and produce speech, extract melodies
from within complex musical compositions, and distinguish intonations of praise from
sarcasm
brainstem auditory nuclei - Answers - -help delocalize sounds through space
-pick up spatial information by:
--> comparing information coming from the 2 ears
--> time of onset of stimulus in one ear vs the other- ear closest to the stimulus hears it
first and at a louder volume; the other ear has a lower volume due to "shadow" created
by the head
olivary nuclei - Answers - localize the source of sound
to localize things in space - Answers - time of onset
loudness
phase
Auditory system uses timing and volume cues to localize sounds in the environment -
Answers - Localize a sound based on its position in medial plane (front, above, back,
below), lateral plane (left, right, front), and distance from us
Localization within medial plane relies on - Answers - o relative orientation of the sound
source
o the structures of the outer ear
, distance cues rely on - Answers - o Evaluation of a sound's frequency spectrum: higher
frequencies diminish more rapidly than lower frequencies
o Loudness: nearby sources provide louder sounds than those far away
-Localization in the lateral plane rely on the fact that there are 2 sets of sensory organs -
Answers - o 2 ears and 2 cochlea
o depending on position of sound, each ear will receive a slightly different signal
Interaural differences = medial, lateral, and distance - Answers - o Provide the
information that the downstream auditory pathway can use to localize the source of
sound
o Interaural Timing: the time it takes a signal to reach the ear on one side of the head
versus the other
o Interaural volume: the amplitude of a sound from one side is diminished when it
reaches the far ear because the intervening head gets in the way
For a continuous sound (rolling growl) auditory system localizes the origin by comparing
the interaural differences in phase timing: the time at which the peak of sound waves
reaches each ear - Answers - for low frequencies and low-wavelength sounds,
Interaural volume differences are used for higher-frequency sounds
-For a sharp, intermittent sound (bark), ears compare timing of the onset of sound -
Answers - Whichever ear is reached first reveals which side the sound is coming from
gradual onset makes difference between 2 ears harder to detect - Answers - useful in
predation
lumbers - Answers - seek commonalities
splitters - Answers - seek differences
vestibular system - Answers - provides important information about head movements,
acceleration, and head positon relative to gravity
-located in the inner ear
-detects up & down in relation to gravity
Core of the vestibular system: adjacent to cochlea in the inner ear - Answers - 3
semicircular canals
2 otolith organs
3 semicircular canals - Answers - sense head rotation and angular acceleration
-there is 1 in each of the 3 planes
-hair cells filled w/ viscous fluid
The inner ear - Answers - -cochlea
-basilar membrane
-organ of corti
-cells
cochlea - Answers - spiral structure made up of 3 fluid-filled tubes wound around a
cone-shape bony core; mission is mechanical amplification of sound
basilar membrane - Answers - runs along length of cochlea; exposed to the fluid waves
triggered by the vibrations of the oval window
-->Fluid vibrations of different frequencies will cause different parts of the basilar
membrane to vibrate, effectively creating a tonotopic map of the incoming frequencies
♣ Small, tight basal end vibrates in response to higher frequency vibrations
♣ Large, floppier apical end vibrates in response to lower frequencies
sounds appear as - Answers - a traveling wave down the basilar membrane
difference in vibrations between tympanic membrane and basilar membrane causes -
Answers - sheer force of hair cells
hair cells transduce information - Answers - act as receptors
Inner hair cells - Answers - code frequencies
-Transduce sound into electrical signals that will be interpreted by the CNS
-limited #, once gone they are gone
-Mechanoelectrical transduction: Motion of hair bundles causes slide relative to each
other tension on tip links pulls open ion channels at ends of links ultra-rapid
depolarization of the cell release of neurotransmitters at the other end of cell
-Opening channels depolarizes cell, closing channels hyperpolarizes cells
organ of corti - Answers - -lies on top of basilar membrane; sharpens sound frequencies
-Packed with 3 rows of outer hair cells (run parallel to inner hair cells)
outer hair cells - Answers - Amplifiers
-Cell's bottoms are lodged in the basilar membrane and their hair bundles are
connected to the overlying tectorial membrane
-In response to oscillating voltage, they physically shorten and lengthen, cycle for cycle,
as fast as the sound itself
-Transduction is mediated by special proteins in the outer hair cell membrane
,-Location allows them to mechanically amplify the incoming sound, making it much
more detectable and sharply tuned --> inner hair cells then receive a much better signal
most frequencies are coded by the - Answers - Place theory or labeled line
-depends on traveling waves
-output of any receptor is clear & tells you exactly what is going on
-cochlea acts as frequency analyzer
-Different neurons carry different, specific information
-The frequency of a stimulus is encoded by the set of afferent fibers that happen to
innervate the hair cells stimulated by that frequency
-Fibers carry information that is "labeled" with a given frequency
-Labeled lines are also used in sensory, visual, vestibular, and somatosensory systems
characteristic frequency - Answers - for a given frequency of sound, only inner hair cells
along distinct portions of the basilar membrane will be stimulated
Spatial separation of vibration frequency breaks down complex sounds into their
component frequencies - Answers - The brain receives all of the individual frequency
components of the sound
8th cranial nerve - Answers - auditory vestibular nerve
-sends information to cochlear nuclei
-"cochlear nerve"; consists of the fibers connecting the cochlear inner hair cells to the
cochlear nuclei in the brainstem
Afferent fiber: neuron transmits signals from the cochlea to the brainstem - Answers -
Each afferent neuron innervates a single hair cell, although each hair cell may be
contacted by 20 or more afferent fibers
tonotopic map - Answers - information in cochlear nucleus is arranged in this way
-organized based on frequencies
-each afferent fiber is activated only by signals of a particular frequency
auditory pathway - Answers - outer ear --> middle ear --> cochlea --> auditory nerve -->
cochlear nuclei (in brainstem) --> olivary nuclei on both sides of the brainstem -->
passes over the lateral lemnisci to the inferior colliculi --> medial geniculate nucleus (of
the thalamus) --> primary auditory cortex (A1)
Primary auditory cortex (A1) - Answers - -in the temporal lobes of the brain
-Tonotopic map
conduction deafness - Answers - Deafness can result from damage to the outer or
middle ear that prevents transmission of sound information to the cochlea
,Sensorineural deafness - Answers - deafness due to damage to the cochlea itself,
usually involves the hair cells
When there is no damage to downstream auditory pathway - Answers - patients can
"hear" useful representations of sounds that they can train their brains to interpret
o Hearing aids: amplify sounds so that impaired structures can perceive and transmit
them
o Cochlear implants: completely bypass patient's nonfunctioning cochlea and transmit
sounds directly to auditory nerve
Damage that affects auditory system downstream of inner ear usually does not result in
deafness - Answers - but rather in deficits in the ability to process sounds
o Damage to A1 on one side of brain (unilateral damage) --> impaired sound
localization
o Damage to higher areas (A1 and A2) --> inability to interpret sound
A1 is responsive only to basic sounds and their modulation - Answers - higher areas of
auditory cortex make it possible to understand and produce speech, extract melodies
from within complex musical compositions, and distinguish intonations of praise from
sarcasm
brainstem auditory nuclei - Answers - -help delocalize sounds through space
-pick up spatial information by:
--> comparing information coming from the 2 ears
--> time of onset of stimulus in one ear vs the other- ear closest to the stimulus hears it
first and at a louder volume; the other ear has a lower volume due to "shadow" created
by the head
olivary nuclei - Answers - localize the source of sound
to localize things in space - Answers - time of onset
loudness
phase
Auditory system uses timing and volume cues to localize sounds in the environment -
Answers - Localize a sound based on its position in medial plane (front, above, back,
below), lateral plane (left, right, front), and distance from us
Localization within medial plane relies on - Answers - o relative orientation of the sound
source
o the structures of the outer ear
, distance cues rely on - Answers - o Evaluation of a sound's frequency spectrum: higher
frequencies diminish more rapidly than lower frequencies
o Loudness: nearby sources provide louder sounds than those far away
-Localization in the lateral plane rely on the fact that there are 2 sets of sensory organs -
Answers - o 2 ears and 2 cochlea
o depending on position of sound, each ear will receive a slightly different signal
Interaural differences = medial, lateral, and distance - Answers - o Provide the
information that the downstream auditory pathway can use to localize the source of
sound
o Interaural Timing: the time it takes a signal to reach the ear on one side of the head
versus the other
o Interaural volume: the amplitude of a sound from one side is diminished when it
reaches the far ear because the intervening head gets in the way
For a continuous sound (rolling growl) auditory system localizes the origin by comparing
the interaural differences in phase timing: the time at which the peak of sound waves
reaches each ear - Answers - for low frequencies and low-wavelength sounds,
Interaural volume differences are used for higher-frequency sounds
-For a sharp, intermittent sound (bark), ears compare timing of the onset of sound -
Answers - Whichever ear is reached first reveals which side the sound is coming from
gradual onset makes difference between 2 ears harder to detect - Answers - useful in
predation
lumbers - Answers - seek commonalities
splitters - Answers - seek differences
vestibular system - Answers - provides important information about head movements,
acceleration, and head positon relative to gravity
-located in the inner ear
-detects up & down in relation to gravity
Core of the vestibular system: adjacent to cochlea in the inner ear - Answers - 3
semicircular canals
2 otolith organs
3 semicircular canals - Answers - sense head rotation and angular acceleration
-there is 1 in each of the 3 planes
-hair cells filled w/ viscous fluid
