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37 Cards in this Set
- Front
- Back
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Parts of the Outer ear |
1. Pinna: cartilege of ear - funnels sound - passive receptor (no muscles) 2. External Auditory Canal: s-shaped - 1/2 cartilage 1/2 skin 3. tympanic membrane: eardrum, elastic membrane that vibrates - protection for middle ear |
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Parts of the middle ear |
Bony levers that help amplify sounds *filled with air! 1. Malleus: "hammer", handle connects to eardrum & head connects to incus 2. Incus: body connects to malleus, long process connects to head of stapes 3.Stapes: oval shaped footplate that connects w/ oval window *these are also referred to as the ossicles! - forms the ossicular chain |
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what does the Eustachian tube do? |
part in middle ear -equalizes pressure across the eardrum -part of the vestibular system -connects to back of the throat |
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Parts of the inner ear |
a.k.a. "baby labyrinth" 1. Vestibular organ: semicircular canals - plays role in balance and body positioning (based off of head movement) 2. **Cochlea: fluid filled bony structure, involved in sensory transduction!!! -part of the auditory system -in temporal bone -general estruture where physical vibrational energy turns into electrochemical signals |
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what are the 2 processes that preserve sound amplitude when converting from air pressure to fluid pressure? 30dB |
1. lever effect 2. condensation effect 3. Resonance effect 4. Directional effect |
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Lever effect |
-preserves 2dB of the 30dB that is preserved -ossicles amplify sound when converting acoustic energy -because of size difference of the handle of malleus (bigger) to long handle of incus, results in small increments of mechanical force -more pressure in fluid because of displacement of incus |
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Condensation effect |
-preserves the remaining 30dB -sound collected by eardrum is channeled through ossicles(small bone) onto footplate of stapes -surface area of eardrum 20X larger - condensation of vibration pressure creates amplification of 25dB |
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Resonance effect |
-all objects have specific resonance property related to mass & elasticity (boosts sound) -sounds at 2500Hz in auditory canal are boosted -sounds at 400-500Hz in pinna -lever & condensation boosted 500Hz-2000Hz |
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Directional effect |
-caused by ossicular chain -reciprocal movement of oval and round window *try to find a video! |
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How the auditory apparatus encode frequency: Frequency theory |
Basilar membrane can vibrate within full range of frequency -Based off of FIRING RATE (strength of action potentials) -vibrate in sync with sound stimulus -amplitude (intensity) is related to size of electrical response in neurons -firing rate mirrors frequency *can't be true!! all or nothing |
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How the auditory apparatus encode frequency: Place theory |
-diff. frequencies produce vibrations whose max amplitude happens at different places (specific) -change in width and tension of basilar membrane produces diff. resonant frequency -each strand has specific frequency -activated by vibrations in cochlear fluid --> creates traveling wave *basilar membrane organized topographically! |
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What are the 3 chambers in the Cochlea? |
1. Scala Vestibuli -connects to oval window! -also connected to stapes (where it starts) b/c of OW -connects with other channel at apex (helicotrema) 2. Scala Tympani - connects with round window at base of cochlea -contains same fluid as (1) both vibrate 3. Cochlear duct/scala media - contains the organ of corti (which is vibrated by basilar membrane) -self contained champers with different fluid (diff. ionic concentration) |
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How does this process analyze complex sounds? |
-decomposes complex waves like Fourier Analysis -vibrations on basilar membrane mimic that of wave (think of fourier spectrum) - exactly! -sine waves is what causes vibrations |
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Auditory Transduction |
converting vibrational stimuli into neural signals -happens in Organ of Corti -spans the length of the basilar membrane/cochlea -in cochlear duct -produces bioelectric response to vibrations of membrane |
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Tectorial membrane of Corti |
-soft jelly structure -attached to stereo cilia of outer hair cells -transfers vibration energy in basilar membrane through organ of court (same with arch) |
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2 cell types in organ of corti |
1. inner hair cells - single row -inner side of arch -extends whole length of cochlea 2. outer hair cells - 3 rows -stereocilia in 2+ parallel rows -outter side of arch -whole length of court -more than inner hair cells (12,000) rows of stereo cilia in v-shape *both contain stereocilia |
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Inner hair cells |
-responsible for transduction! -moves in direction of shearing force -tip links tighten when stereo cilia move to the right (outside) - opens ion-gated channels -causes depolarization -neurotransmitter is released from hair cell into cochlear nerve - creates action potential!! *carried to higher processes |
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What does the depolarization of inner hair cells do? |
1. opens ion channels even more = greater depolarization 2. increase in Ca leads to release of neurotransmitter at base of heir ell (connected to cochlear nerve) *action potential is produced in nerve |
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What is the role of the outer hair cell? |
* review! |
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what is the hierarchy of the neural cross over? |
right side: 1. cochlea (of right side) 2. Spiral ganglion of right side (monaural neurons) 3. Cochlear nucleus (gos to SO + so left + ic left and right) 4. Superior olive (goes to IC) 5. Inferior colliculus (goes to ic left + MGN right + mgn left 6. MGN 7. Auditory cortex (from MGN) |
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Auditory fatigue |
*variability in hearing loss -momentary reduction of hearing due to exposure of intense sound or drugs i.e. concerts |
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Hearing loss |
reduction in auditory sensitivity/perception b/c/ of deficiency in sound processing |
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Hearing dysfunction is described by site of damage: where does damage normally happen? |
1. conductive loss: outer or middle ear are affected, reduced transmission 2. Sensorineural loss: damage to cochlea or nerves in inner ear *both lead to reduced perception |
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Hearing dysfunction is described by age onset: |
1. Congenital hearing loss: genetic cause/problem associated w/ birth process 2. Acquired hearing loss: happens later in life |
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Causes of hearing loss: CONDUCTIVE LOSS |
-affects mechanical conduction of sound -may be due to wax, infection, otosclerosis |
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middle ear infections (otitis media) (conductive loss) |
1. inflammation of eustachian tube - causes imbalance in pressure across ear drum -changes vibrational properties of the eardrum 2. Fluid build up - infection -interfere w/ conduction of ossicles * otitis media is more common in children |
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Otosclerosis (conductive loss) |
-inherited bone disease --> abnormal development & function of ossicles (conductive loss) -calcium in issicles creates impairment in their movement (especially in stapes) |
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Causes of hearing loss: SENSORINEURAL LOSS |
-damage of heir cells (they don't regenerate) -causes = some ototoxic drugs (can lead to tinnitus), head injury, tumors, disease, overexposure to noise (noise-induced hearing loss) -damages transductional mechanism
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at what amplitude are sounds considered painful? |
80dB = dangerous 120dB = painful |
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2 major hereditary causes of hearing loss |
1. Usher syndrom 2. Wardenburg syndrom + 3. Aging - Presbycusis |
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Diagnosis/treatments |
1. bone conduction test (ring test) -use a tuning fork, tap in air and on bone behind ear -if perceived louder in air = normal hearing -if sound only heard when touching bone = conduction hearing loss -if sound not heard at all = sensorineural hearing loss |
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Otolaryngologist (ENT) |
clinical diagnosis of auditory disorders |
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Audiologist |
evaluates hearing function - level of hearing loss - can uses test previously mentioned and prescribes hearing enhancement mechanisms |
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Hearing aids |
-only effective is sensory function in choicely is NOT lost -amplifies incoming sounds -collected through mic and speaker delivers sound to ear *useful for speech comprehension |
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Cochlear implants |
-used for sensoryneural damage - hair cell function is totally lost -mic converts sound signal into electrical signal -delivers it through inner ear -takes over transactional mechanism of cochlea and stimulates auditory nerves itself 2 types of implants : 1) single channel 2) multi channel |
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single channel implants |
-delivers electrical signal through single electrode to nerve fibers - not rich content of sound frequency -accoustice warning - does not restore normal hearing |
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multi channel implants |
decodes incoming sound into parallel channels (own characteristics of frequency representation) -richer content |
