6A: Hearing (Audition) Flashcards
Which ear structures are considered part of the external/outer ear?
The auricle/pinna and external auditory canal are considered part of the external/outer ear.
The _____ or ______ refers to the visible part of the ear, wh collects, mechanically transforms (amplifies), and directs sound into auditory canal.
The auricle or pinna refers to the visible part of the ear, wh collects, mechanically transforms (amplifies), and directs sound into auditory canal.
- Humans: Filters/selects for sound waves in the freq range of human speech.
- Works t/g w middle ear to amplify sound by 22x (↑ 10-15 dB in freq range of 1.5-7 kHz).
The tympanic mem (also “myringa”) is commonly referred to as the _______. Its key function is to transmit sound fr _____ to ______ to ______.
The tympanic mem (also “myringa”) is commonly referred to as the ear drum. Its key function is to transmit sound fr air to ossicles to inner.
- I.e. converts/amplifies sound wave to vibration in fluid.
Wh ear structures are considered part of the middle ear?
Middle ear: incl ossicles; region b/w tympanic mem and oval window of cochlea.
- primary func: xfr acoustic energy fr compression waves in air to fluid-filled mem waves in cochlea.
What are the three small bones that transfer vibrations of eardrum into waves in fluid/mems of inner ear?
Ossicles - Malleus (hammer), Incus (anvil), and Stapes (stirrup); transfer vibrations of eardrum into waves in fluid/mems of inner ear.
- Recall: part of middle ear.
The ___________ is the passageway fr back of throat (nasal cavity; nasopharynx) to tympanic cavity of middle ear; equalizes pressure on both sides of eardrums; cause of “ear popping” in pressurized environ.
The eustachian/auditory tube is the passageway fr back of throat (nasal cavity; nasopharynx) to tympanic cavity of middle ear; equalizes pressure on both sides of eardrums; cause of “ear popping” in pressurized environ.
Wh ear structures comprise the inner ear?
Inner ear – oval window, round window, cochlea, semicircular canals (vestibular sys, i.e. balance).
The ______ is a fluid filled, spiral/snail-shaped structure containing three sections: two fluid-filled canals (_______ and ______) and the Organ of Corti; converts sound waves into __________.
The cochlea is a fluid filled, spiral/snail-shaped structure containing three sections: two fluid-filled canals (vestibular and tympanic) and the Organ of Corti; converts sound waves into electrical impulses.
- Tonotopically organized (basilar tuning) - high freqs transduced nearer the base; low freqs nearer apex.
The cochlea is said to be tonotopically organized (basilar tuning). What does this mean in terms of where sounds are transduced?
Tonotopically organization (basilar tuning) - diff freqs interact w diff locations on the structure.
- Base—closest to outer ear—is stiff/narrow → high freq sounds transduced.
- Apex/top is more flexible/wider/loose → low freq sounds transduced.
Perilymph and endolymph are types of what?
Perilymph/Endolymph - basilar/cochlear fluid.
The __________ is the thin strip of tissue w/i cochlea; contains hair cells wh serve as sensory receptors for auditory system.
The basilar membrane is the thin strip of tissue w/i cochlea; contains hair cells wh serve as sensory receptors for auditory system.
What is the term for the sensory organ of hearing?
Organ of Corti - the sensory organ (epithelium) of hearing, i.e. transduces auditory signals and minimizes hair cells’ extraction of sound energy.
- Situated on basilar mem; contains four rows of hair cells wh protrude fr surface.
- Think of it like the body’s microphone.
- Detects pressure impulse wh travel along auditory nerve to brain.
Where is the organ of corti located?
The organ of corti is situated on the basilar mem: a thin strip of tissue w/i cochlea.
________ are mechanosensory receptors covering the basilar mem w/i the cochlea. They are topped w ________ (bundles of ________), wh transduce sound waves into __________.
Hair cells are mechanosensory receptors covering the basilar mem w/i the cochlea. They are topped w stereocilia (bundles of kinocilium), wh transduce sound waves into elec/nerve impulses.
How are stereocilia arranged on hair cells?
Stereocilia (bundles of kinocilium) are arranged fr shortest on periphery to longest at center → superior tuning capability.
Kinocilium—wh comprise stereocilia—are connected by cadherin structures called ______, wh open/close K+ channels on hair cells.
Kinocilium—wh comprise stereocilia—are connected by cadherin structures called tip links, wh open/close K+ channels on hair cells.
As wavelength ↑ → frequency (↑/↓/-) → (↑/↓/-) penetration into cochlea.
As wavelength ↑ → frequency ↓ → ↑ (deeper) penetration into cochlea.
What feature of ears allow for differentiation b/w mult simult freqs?
Tonotopic org/mapping/basilar tuning enables differentiation b/w mult simult freqs bc wave travel diff lengths in cochlea.
- As wavelength ↑ → frequency ↓ → ↑ (deeper) penetration into cochlea.
- Mapping: sound enters cochlea → travels/activates hair cell that matches its freq → mapped to partic part of brain.
The typ stated range of human hearing is b/w ____ to ____; most sensitive around _____.
The typ stated range of human hearing is b/w 20 Hz to 20 kHz; most sensitive around 2-5 kHz.
As humans age, we typ lose sensitivity to (higher/lower) freqs.
As humans age, we typ lose sensitivity to higher freqs.
As loudness ↑ → vibrations generate (more/less) freq APs.
As loudness ↑ → vibrations generate more freq APs.
The _____________ is part of the temporal lobe; receives all info fr cochlea, sep’d into regions wh correlate w range of freqs.
The primary auditory cortex is part of the temporal lobe; receives all info fr cochlea, sep’d into regions wh correlate w range of freqs.
- Recall: tonotopic mapping → diff freqs send APs to diff regions of primary auditory cortex.
- Think: Tuba Luba = Temporal Lobe
Wrt hearing, what is rarefaction?
Rarefaction is the opp of compression.
Ea sound wave (phonon) is half compressed and half rarefaction.
- Alternating phases of a sound wave set the tympanic mem in motion → sympathetic vibration thru ossicles → basilar fluid in cochlea → hair cells → primary auditory cortex.
________ are the instrument used to measure human hearing; produce _______.
audiometers are the instrument used to measure human hearing; produce audiograms.
Describe the basic process of auditory transduction, up to displacement of basilar/cochlear fluid.
Auditory transduction:
- Sound wave hits pinna (amplifies/filters)
- Funneled into auditory canal (amplifies)
- Vibrates tympanic mem (eardrum; amplifies)
- Vibrates ossicles (MIS)
- Oval window (attached to stapes) moves and causes movement of round window
- Displacement of cochlear fluid.
Describe the basic process of auditory transduction, fr displacement of basilar/cochlear fluid to AP gen.
Auditory transduction:
- …displacement of cochlear fluid.
- Basilar mem (in tympanic duct) presses against hair cells (Organ of Corti) as perilymphatic pressure waves pass
- Stereocilia atop hair cells move w fluid displacement.
- Top links open K+ channels → K+ flow fr endolymph into hair cell → hair cell depols → v-gated Ca2+ channels open.
- Activates spiral ganglion cells → triggers release of glutamate.
- AP sent thru auditory nerve → into auditory cortex.
Describe the path of the sound wave thru the basilar/cochlear fluid.
Wave of cochlear fluid travels fr oval window (base) to the apex then back to the round window (base), i.e. diff canal used for return path.
APs are generated as top links connecting adj kinocilium open mechanically gated K+ channels → hair cell depols → v-gated Ca2+ channels open → release of glutamate. When/how does AP generation terminate for an individual sound wave (phonon)?
The wave repeatedly travels thru cochlear fluid (oval → apex → round)—generating APs—until the energy of the sound wave dissipates.
Hearing (audition) is typ thought of as Air Conduction (AC) hearing, meaning sound waves come fr air in surrounding environ. How else might auditory impulses be generated?
Stim can also occur via direct vibration of cochlea fr skull: Bone Conduction (BC) hearing; complementary to typ pathway: Air Conduction (AC) hearing.
- Both stim basilar mem in same way.
Wh theory describes how tonotopic organization maps diff pitches (freqs) to diff regions of primary auditory cortex?
Place theory - perception of sound deps on where ea component freq produces vibrations along the basilar mem; based on tonotopic org of primary auditory neurons.
Cochlear implantation is surgical procedure that restores some degree of hearing to individuals w _____________________.
Cochlear implantation is surgical procedure that restores some degree of hearing to individuals w sensorineural narrow hearing loss (nerve deafness).
Describe the general auditory transduction pathway for individuals w cochlear implants.
Sound → microphone → speech processor → transmitter (external) → receiver (internal) → stimulator → cochlea → cochlea converts electrical impulse into neural impulse → brain (primary auditory cortex; temporal lobe).
What is interaural time difference?
describes the diff in time it takes a sound to reach the left vs the right ear.
What is the acoustic shadow?
region of reduced amplitude of a sound because it is obstructed by the head.
What is the interaural level difference?
describes diff in sound pressure level b/w ears.
Head dampens overall sound to far ear and ↓ intensity of high freq tones due to acoustic shadow, but not low freq tones.
What is the McGurk effect?
McGurk effect - perceptual phenomenon; demonstrates interaction b/w hearing/vision in speech perception.
- Occurs when auditory component of one sound is paired w visual component of another sound → perception of third sound.
