Electrophysiology > ANATOMY PORTION > Flashcards

ANATOMY PORTION Flashcards

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1
Q

How does the transmission of sound works arriving at the round window?

A

Sounds arrives at the round window, vibrates the fluids of the inner ear and basilar membrane creating a traveling wave. The brain can only interpret electrophys sounds

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2
Q

Basilar membrane moves in response to ….

A

Sound causing movement/shearing of hair cells

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3
Q

Basilar membrane is organized ____? HF located where? LF located where?

A

Tonotopically; base; apex

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4
Q

Hair cells have different

A

Morphology, interaction, and function

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5
Q

Outer hair cells

A

Three rows; efferent (exiting) pathway

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6
Q

Inner hair cells

A

One row; help predominantly for hearing (primary source of hearing); afferent pathways (travels up toward the brain from the ear); sensory receptors

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7
Q

What percentage of auditory nerve fibers to the the brain arise from the inner hair cells?

A

95%

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8
Q

Why do nerve endings exit the cochlea

A

To form cranial nerve eight (vetibulo-cochlear nerve or CNVIII)

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9
Q

CNVIII synapses

A

At the brain stem (where information travels higher to )

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10
Q

Where is sound processed

A

In the auditory cortex

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11
Q

Where is the Heschl’s gurus located?

A

In the temporal lobe

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12
Q

Subcortical auditory pathways

A

Form a complex network of cell types, organizations, and interconnections

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13
Q

How is tonontopicity maintained?

A

In the auditory cortex

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14
Q

Neural redundancy is evident

A

CANS processes information in overlapping ways

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15
Q

Order of the central auditory nervous system (CANS) as sound travels up?

A

Cochlear- Brianstem- thalamus- auditory cortex

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16
Q

Order of the to the auditory cortex as sound travels up?

A

Cochlear- cochlea nucleus (brainstem)- superior Oliver complex (brainstem)- lateral meniscus (pons)- inferior colliculus (midbrain)- medial genicate body (thalamus)- auditory cortex (brain; temporal lobe)

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17
Q

Superior Olivary complex

A

Important for localization, input is compared from both ears

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18
Q

Lateral Lemniscus

A

Brings lower layers up, sound up from the SOC to inferior colliculus, important for processing, relaying sound, and detecting changes in sounds like rhythms

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19
Q

Medial genicualte body

A

Received signals from inferior colliculus and brings it right up to auditory cortex is where sound is meaningful, this is what we are hearing and where sound is being interpreted

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20
Q

Auditory Evoked Potentials (AEPs)

A

Involve the process of stimulating (evoking) response/potentials from the auditory system (happens within the auditory system)

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21
Q

What is an electrical signal elicited as a result of auditory stimulation

A

Auditory Evoked Potentials (AEPs)

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22
Q

Auditory Evoked Potentials (AEPs) what are generated and analyzed?

A

Sounds are presented and brain waves (electrical potential) are generated. Waves (waveforms) are analyzed

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23
Q

Auditory Evoked Potentials (AEPs) responses

A

Are time locked (where and when they are going to happen)

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24
Q

Auditory Evoked Potentials (AEPs). Simulation that elicits a series of electrical signals (potential) within the ear and nervous system can be used to

A

Assess hearing, intraoperative monitoring, and neurophysiologic research

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25
What do we use Auditory Evoked Potentials (AEPs) for
Record neural activity specifically focuses on the auditory system
26
Why is Auditory Evoked Potentials (AEPs) important
Early detection and diagnosis of auditory dysfunction, site of lesion testing (retro cochlear disorders), intraoperative monitoring, vestibular (contributes to the diagnosis of pathology), useful for difficult to test patients
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Interaoperative monitoring
Patient does not have to activity be involved/participate
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Early Auditory Evoked Potentials (AEPs)
Electrocochleography (earliest of all because its response arises from the cochlea itself) ABR arises from regions of the brain stem
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Middle Auditory Evoked Potentials (AEPs)
AMLR auditory middle latency response (ABR and ALR)
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Late Auditory Evoked Potentials (AEPs)
P300 ALR auditory late response going it have the longest latencies
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Latency
Time after stimulation (X-axis of chart) Longer latency= longer time for sound to travel through the auditory system Measures in ms ( time at which responses peaks)
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Amplitude is measured in
Microvolt uV (from peak to drop) Lower intensity gives smaller response High intensity gives larger response
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Far field recordings
Made far from where the response is generated ex surface electrodes *this is most recordings
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How is recording information conveyed
From the auditory structures through body tissues, fluids, bones, and skin
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Far field AEP electrodes for recordings are usually placed where
Scalp or behind the mastoid
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Near field recordings
Made close to where the response is generated General invasive (used in more surgical cases) Sensitivity to electrode placement
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Near field AEP electrodes for recordings are usually placed where
On or very close to the neural generator
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Benefits to near field recording
Much better waveform repeating bc electrodes are right above where the response are formulating
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Millisecond
One thousandth of a second
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Microvolt
One thousand of a millivolt (one million of volt)
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Are AEPs quick or slow responses
Really quick, AEP measures change over time
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Since AEPs readings are small what can we do to help identify the response?
Amplify to make the response large enough, signal averaging, noise of a response not of interest, latency, amplitude
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Signal averaging
Synchronization of stimulus onset and response; several responses are recorded and averaged to minimize noise
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What’s considered noise
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What’s considered noise
Non auditory brain activity, actual noise, electrical interference, and patient movement
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What is latency measured in. X or Y axis?
ms X-axis
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The time at which the response peaks
Latency
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Measured distance between peak and trough
Amplitude
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What is amplitude measured in? X or Y axis?
Microvolts Y-axis
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What affects amplitude response
Intensity level
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AEP transducers
Most AEPS elected by brief acoustic transient sounds presented via transducer (head phones, inserts, bone oscillator)
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Which transducer is preferred to AEPs? Why?
Inserts bc they reduce ambient noise, prevent collapsed canals, infection control and have larger interaural attenuation
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what patient factors could affect recordings?
age, gender, body temperature, state of arousal (sleep much better responsw bc of eye movement), drugs, hearing loss
54
what is the most common stimulus type for AEPs? How come?
clicks and tone burst creates simultaneous firing of multiple neurons of the auditory nerve activating different areas of the cochelar all at the same time; happens quickly and breif(short). ASSR will use an amplifier of modulator tone (long and continuous) AML tone burst or even speech stimuli
55
Clicks
most commonly used for ABR broad spectrum well suited for generating synchronous firing neurons brief (.1 ms) not continuous not freq specific (encompasses a wide ragne of freq and all regions of the cochlea are activated
56
Tone burst
brief (think of a pure tone on audiometer) not continuous modifer pure tone has become standard care for ABR in infants and young children (no patient participation) freq specific (500, 1000, 2000, 4000 Hz) - can be used to define degree and confirguration of HL can be important for early intervention uses 5 1 2 4 and estimateions of threshold ??
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Chrips
new stimuli sound similar to tone burst provides larger ABR amplitude - low freq nad high freq stimulus - low freq - presented before high freq more confident(accurate) identification fo waves ABR reduce test time (responses faster)
58
Duration
length of acoustic stimulus from beginnign to end sum of onset (rise time) - plateau time, and offset (fall time)
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intensity
how loud the stimulus, amplitude increases with increasing intensity, latency decreases with increasing intensity (will see latency earlier with increasing intensity)
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rate of stimulus
freq in which the stimulus is presented
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slow rate of stimulus
more effective, clearer waveform (better morphology), identify latency much easier, activate certain areas of the brain stem (thalamus and auditroy cortex)
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fast rate of stimulus
delay responses, activated cochlear lower brainstem CNVIII, less clear morphology
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number of stimuli
more stimuli = more time to average response, better chances at a good result and may be referred to as sweeps
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polarity 3 types
rarefaction (neg), condensation (pos), alternating (switches between the first two, using may limit response we are not interested in testing for)
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Electrocochleography
is an electrophysiological technique or evoked potential of recording the electrical responses that occur in the cochlear hair cells and auditory nerve in response to acoustic stimulation which is why ECochG is dependent on the integrity of hair cells. If damaged you may not be able to get recording or get a non-repeatable one
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electrocochleography creates what?
electrocochleogram (name for the waveform we see)
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Wever and Bray
1st recorded or creation of the electrocochleogram waveform from a cat's brain activity recording acoustic acitivity from a cat's cochlea.
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What was significant about Wever and Bray's
1930 first wave takes place, cats different acoustic stimuli, and discovery of the cochlear microphonic
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What year did ABRs take place?
70s
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4 main purposes of using an ECochG
diagnosis/assessment/monitoring of Meniere's Disease Enhancement of ABR wave 1 Monitor cochlear and 8th nerve function during surgical procedures (semicircular canal) contribe to diagnosis of auditory neuropathy (least popular) EcochG alone will not help diagnose
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Latency for an ECochG
.2-4.0 ms within 10ms phrase, will see way before 20ms
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In ECochG, what intensity signal is used to detect?
high intensity 90 to 100 dB
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What are th/e generators for ECochG? Cochlear microphonic? SP? AP?
cochlea and 8th nerve (ECochG is earliest of all responses) OHC OHC / >50% IHC Afferent fibers in dital/cochlear part of CNVIII
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ECochG, what do you always mark
SP and AP
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what are the components of ECochG
cochlear microphonic, SP, AP, baseline (0 ms)
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what does the baseline in ECochG do?
serves to identify where the other two peaks begin, right around 0 ms mark. One of the first things you will see. 1 1/2 ms between 1 and 2 ms
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cochlear microphonic
instantaneous response (no delay) presynaptic response bc it is an instantaneous Alternating current electrical potential believed to originate mainly from the sum of extracellular components arising from IHC’s and OHC’s.
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SP
arises from hair cells of the cochlea. direct current potential. can be evoked by transient stimuli (clicks, tone burst) Usually appears as a bump or a ledge on the beginning of the slop of the action potential (AP) or as a distinct wave peak
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Patients with Meniere’s Disease will have an what SP
enlarged
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Endolymphatic Hydrops
swelling of the membranous labyrinth because of increased production or decreased absorption of endolymph
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AP or compound action potential (CAP)
Post-synaptic response This response is from the auditory nerve; small vestibular component response Larger amplitude than SP AP = Wave I of ABR Consists of N1 and N2 (sometimes detected) same as wave 1, wave 2 Same as wave 1 and wave 2 of ABR
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Latency of AP can be seen around
1.5 ms
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WIll HL effect an ECochG?
yes, more severe HL less likely the ECochG will look easy/clear to interpret (poor morphology)
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morphology measures
SP/AP ratio, calculating a percentage
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WHen the SP increases in size and the CAP decreases in size
a disorder/patholgoy progresses
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Transtympanic TT
invasive - thin metal needle electrode inserted through TM requires physican to be present
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advantages of TT
larger amplitude (largest), fewer signal averages (quicker and stable responses), can get preinformation for CI
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disadvantages of TT
need MD supervision Anethsia
89
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