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102 Cards in this Set
- Front
- Back
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Ganglia |
Bundles of gray cell bodies in peripheral nervous system
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Tracts |
Bundle of myelinated axons in Central nervous system |
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Reflexes |
Pathway from motor nerves to spinal cord then |
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Myelin |
White fatty sheath protecting neuron fibers (the axons and dendrites) Provides insulation during electrical transmission |
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The 8th Nerve |
Afferent Bipolar Tonotopic 1 inch long Ten 8th nerve fibers from each inner hair cell go to the brain Cochlear has 3000 inner hair cells (arranged in 1 row) Total of 30,000 8th nerve fibers |
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As the stapes is pushed into the oval window... |
fluid pressure builds in the Scala vestibuli as it tries to squeeze thru the helicotrema |
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Asymmetrical wave |
The steep wavefront faces the Apex which is more mass |
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Background noise |
Usually low frequency and Speech is usually high frequency Upward spread of masking causes the lows to mask the high frequencies |
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How does acoustic reflex occur in both ears |
Because of decussation, crossover in the brainstem |
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How many IHC and OHT are in the cochlea |
3000 inners 12,000 outers |
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How many stereocilia do the hair cells have |
Inners have 50 Outers have 100 |
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How are outer hair cells arranged |
3 rows at base 4 rows in mid 5 rows at apex |
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The acoustic reflex |
Reduces upwards spread of masking Attenuates by 14 dB Response time of 60-120 milliseconds |
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Middle ears adds |
30-35 dB to frequencies between 500-5000 Peaking at 2000 |
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Outer ear adds |
20-25 dB to frequencies between 1000-4000 Peaking at 2700 |
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Low brainstem |
Medulla Spatial sound recognition Houses pair of cochlear nuclei (CN) |
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Middle of brainstem |
Pons Houses pair of superior olivary complex First place to receive info from both ears important for 3 things: -For acoustic reflex and reflex arc -For localization of sound -Contains Olivocochlear bundle |
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Localization of sound |
In the Superior Olivary Complex Compares time of arrival for lows below 1500 Hertz Compares intensity for highs above 1500 Hertz |
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Olivocochlear Bundle |
Efferent Nerve of 1800 fibers Sends info from brain to ears Cell bodies of OCB housed in SOC |
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Inner hairs cells move by way of: |
The tectoral membrane being pulled down by outer hair cells |
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Inner hair cell damage |
Neural hearing loss Poor speech recognition |
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Outer hair cell damage |
Sensory HL Presbycusis Noise induced Mild to moderate SNHL |
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Inner hair cells sense |
Sounds softer than 50-60 dB/ conversational speech levels |
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Helicotrema |
Small space at Apex of cochlea Joins Scala vestibuli and Scala tympani Perilymphatic pressure builds |
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Stapedius muscle |
Innervated by facial nerve The 7th cranial nerve Short (7 mm) and strong muscle Involved in acoustic reflex |
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Tensor tympani muscle |
Innervated by trigeminal nerve The 5th cranial nerve Long (25 mm) and weak muscle |
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Ampulla |
Detect angular acceleration/ head position and turning Have cristae with type 1 and 2 haircells |
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Electronystagmography |
Test for vertigo Involves sensors for eye movement with water pressure in ear canal |
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Benign paroxysmal vertigo |
When otoliths fall off of otolithic membrane |
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Outer ears |
If u have 1 ear you lose 5 db If you no outer ears you have 10-20 dB of high frequency HL |
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Reflex Arc |
Afferent/ Efferent Loop Loud sound to cochlea to 8th nerve to cochlear nucleus to superior Olivary Complex To 5th nerve to tensor tympani muscle and to 7th nerve to stapedius muscle for the acoustic reflex to attenuate the loud sound |
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Acoustic reflex intensity |
Pure tones at least 80 dB SPL Complex noise at least 60 dB SPL |
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Upper brainstem |
Midbrain Links vision and sound, localization Inferior colliculus Superior colliculus |
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Inferior colliculus |
Largest auditory brainstem center Forms 2 mounds 1 inch from CAN at pontomedullary junction, to IC at midbrain (top of stem) |
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Efferent |
From cochlear nucleus to contralateral superior Olivary Complex to outer hair cells |
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Afferent |
From inner hair cells to 8th nerve to cochlear nucleus |
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Olivocochlear nerves |
Outer hair cells each have a single OCB fiber Many inner hair cells will share a single OCB nerve fiber |
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8th nerve fibers |
Inner hair cells each have an 8th nerve fiber Many outer hair cells share a single 8th nerve fiber |
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Heschels Gyrus |
Primary auditory cortex bes Pull apart Silvian fissure to see it Bigger on left side for most people Deep inside temporal lobesPull apart Silvian fissure to see itBigger on left side for most peopleCortical area- first area of auditory perception/ conscious awareness Cortical area- first area of auditory perception/ conscious awareness |
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Medial Genicular Bodies |
lamus just below corpus callosum Located in Thalamus just below corpus callosumGrand Central Station for sensory input except olfaction (smell) |
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Ipsilateral versus Contralateral |
Ipsilateral is nerve communication on the same side of brain Contralateral is nerve communication on the opposite side of brain |
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CANS |
Central Auditory Nervous System Pairs of nuclei, (gray matter), in the brainstem and brain, connected by tracts, (white matter) Each nucleus is tonotopic Lots of decussation |
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Modiolus |
Bony center of cochlea |
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Stria vascularis |
Blood supply to Scala media |
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Aphasia |
Stroke Burst blood vessel in brain Usually effects left side of brain in auditory association cortex Either in Wernicke or Brocas area |
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Wernicke's Area |
Located near occipital lobe Linguistic meaning assigned to language Damage causes fluent aphasia/ stroke Sad, can speak without making sense |
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Brocas area |
Located near frontal lobe Controls motor movement of mouth and tongue Damage causes dysfluent aphasia/ stroke Knows what to say but cannot articulate properly |
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Chorda tympani |
Nerve branch from facial nerve controls taste on part of tongue |
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Nuclei |
Bundles of gray cell bodies in Central nervous system |
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8th nerve tunnel |
From spiral ganglia in cochlea thru the Internal auditory meatus to the brainstem at pontomedullary junction |
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CAPD |
Central Auditory Processing Disorder |
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Auditory Brainstem Response |
Audiologists scope Electrophysical test for 8th nerve tumor |
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Vestibule |
Cavity of inner ear containing equilibrium organs and entrance of cochlea |
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Neuron |
Nerve cell including cell body, axon (sends info) , dendrite (receive info), synapse |
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Kemp |
Discovered otoacoustic emissions proving outer hair cells are active/ active traveling wave in 1980s |
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Gold |
Suspected an active traveling wave in 1940s-1950s Gold was proved right in '80s with Kemps discoveries |
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Békèsy |
Discovered the passive traveling wave in cadavers in 1940-1950 Nobel prize 1961 Dismissed Gold's theory of active outer hair cells |
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Hemholtz |
Discovered the cochlea being tonotopic in 1800s |
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Dysacusis |
Distortion of an auditory signal associated with neural HL, poor word recognition |
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What affects the traveling wave? |
Intensity |
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Otoacoustic emissions exit via: |
The oval window and external ear canal |
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Atresia |
Congenital closure of a normally open canal |
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Stenosis |
Partial closing, or narrowing of the canal |
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Synapse |
Area of communication between neurons |
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Brainstem |
The spinal cord within the cranium Contains 3 parts: midbrain at the top, pons in the middle, and medulla at the bottom |
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Tonotopic nerve placement |
Fibers at the apex are on the medial side of the cochlea for low frequencies Fibers on the lateral side of cochlea are for high frequency |
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Pons |
Bridges the brain hemispheres and connects medulla with midbrain |
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Concha resonance |
5000-6000 Hz |
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Axons |
Unmyelinated within the cochlea Myelinated after the spiral ganglia |
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Interneuron |
Integrate sensory and motor neurons, about 1 trillion |
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Sensory and motor neurons |
Sensory neurons are bipolar Motor neurons are multipolar |
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Neural threshold |
The amount of sound required to increase the rate of neural firing |
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Characteristic Frequency |
Downwards point shows the Hz where least amount of dB is required to get the neuron to fire
A different tone must have more intensity to get the same neuron to fire Damage to OHC causes elevated rounded peaks |
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Sending information to the brain |
New info goes to the upper brain to develope a pattern if repeated Designated to lower brain after established |
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Most SNHL is caused by |
Outer hair cell damage |
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Sheared |
When inner hair cells bend due to outers pulling the tectoral membrane downwards |
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Men versus women HL |
Men have a steeper sloping HL and more NIHL Women have gradual hl and strial HL |
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Hearing aids restore: |
Loudness Cannot restore sharpness |
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Purpose of inner ear |
Transduce hydraulic energy into electrical energy |
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Purpose of middle ear |
To transduce sound wave energy into mechanical energy |
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Basilar membrane |
Ground for organ of Corti Very stable held tight between spiral lamina and spiral vascularis |
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Pilloried mechanoreceptors |
Fixed at bottom, tied at neck (Looks like golf tee) Specialized epithelial cells Hybrid between neuron and epithelial cell |
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Travelling Wave |
Horizontal movement of perifluid Results in vertical movement of Scala media through reissners and basilars membrane |
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Types of presbycusis |
Sensory outer hair cell damage Neural inner hair cell damage |
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Impedance matching function |
Middle ear transformer overcomes the impedance mismatch by 33 dB - condensation effect/ areal ratio 17x - lever action of malleus/ incus 1.3x - curved membrane buckling of tympanic membrane 2x
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Utricle/ Saccule |
Detects linear and sideways acceleration/deceleration Utricle is larger, saccule smaller Located in vestibule with perilymph Contains macules with type 1 and 2 hair cells for |
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Orthogonal planes |
Canals are situated at 90° to one another |
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Cochlear size |
35 mm long 5 mm tall 2.5 turns (snail-like) auger in bone "Tip of pinky finger" |
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Cochlear duct |
Scala media Membranous labyrinth Filled with endolymph |
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Dichotic listening assumes: |
Left temporal love is dominant for language Contralateral tracts suppress ipsilateral tracts Testing uses numbers 1 to 9 except for 7, since it's a double syllable word. The numbers are simultaneously presented to both ears and patient will try to tell you what they've heard. |
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2 crossover areas in brain |
Low brainstem Corpus callosum |
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Pairs of nuclei from top down |
Heschels Gyrus Medial Geniculate Bodies Inferior Colliculus Lateral Lemniscus Superior Olivary Complex Cochlear Nucleus
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Frontal Lobe |
Reasoning and thought |
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Occipital Lobe |
Vision |
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Temporal Lobe: |
Speech and Hearing |
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Parietal Lobe |
Integration and association |
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Nuclei Areas of Brainstem |
Corpus Callosum Thalamus Midbrain Pons Medulla |
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Link Areas with Nuclei |
Corpus Callosum: Heschels Gyrus Thalamus: Medial Geniculate Bodies Midbrain: Inferior Colliculus Pons: Lateral Lemniscus, superior Olivary Complex Medulla: Cochlear Nucleus |
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Right Ear Advantage |
Slight REA is normal in dichotic digits test because left lobe dominant crossover in most people Major right ear advantage indicates CAPD, because improper myelination of corpus Callosum |
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CANS Diagnoses |
Usually poorly defined and over diagnosed Boys moreso than girls labelled CAPD involves trouble listening, not hearing |
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Cochlear Nucleus |
Where 8th nerve leads to first Located at pontomedullary junction, on brainstem surface Important in visualization of distance of sound |
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First place to receive info from ears |
SOC Receives ipsilateral and Contralateral tracts from CN |
