audiovestibular system reflexes and EP Flashcards
(30 cards)
two main auditory reflexes
startle and acoustic reflex
startle reflex
the effect a loud sound has and how it causes a startle
-formerly used to test infants (moro reflex)
-basic startle reflex for adults
startle reflex pathway
cochlea to CN 8 to cochlear nucleus (AVCN) to VNLL then to reticular pontine formation to medial longitudinal fasiculus out to spinal cord
what happens with the startle reflex when it goes out to the spinal cord?
lower motor neurons are stimulated which allow for a quick, tense movement
what is involved within the startle reflex
-cortical areas (A1) to receive the signal
-limbic system and ANS (autonomic nervous system) for emotions (fight or flight)
-IC and SC to help orient the head
acoustic reflex
sound to one ear generates a reflex in both ears
-ipsilateral and contralateral reflex’s
ipsilateral reflex pathway
3 arch : CN 8 to antero-ventral cochlear nuclei to facial motor nucleus to stapedial muscle
4 arch : nerve fibers to antero-ventral cochlear nucleis to medial superior olive to facial motor nuclei to stapedial muscle
ipsilateral acoustic reflex threshold testing (ART)
playing a sound in one ear and testing the reflex in the same ear
-testing the health of the ipsi response
contralateral reflex pathway
1st route : CN 8 to antero-central cochlear nuclei to medial supeior olive crossover to facial motor nucleus to stapedial muscle
2nd route : CN 8 to antero-central cochlear nucleus crossover to medial superior olive to facial motor nucleus to stapedial muscle
contralateral acoustic reflex threshold testing (ART)
playing a sound in one ear and testing the reflex in the other ear
-testing to see if sound can travel over
reflex decay
play loud sound above reflex threshold for 10 seconds
-tells us about the integrity of CN 8 fibers to see if they can hold the reflex for 10 seconds
recruitment
abnormal growth of loudness
-can occur as a result from a certain HL where outer hair cells are damaged or lost and so higher frequencies will still sound loud but those lower ones are affected
evoked potential
(electrical response of the brain to a sensory stimulus)
ability to measure the bioelectrical activity of the cochlea, peripheral nerves and central nervous system nuclei and neurons
bioelectric energy
neurons create bioelectric energy
-the current in the extracellular space creates an electrical or potential field
-this field has negative polarity at one end and a positive polarity at the other end
EEG montage
where we are playing electrodes and mapping them out
-the 10-20 system EEG montage
within the EEG montage, even refers to what side? odd?
even - right
odd - left
Fpz
prefrontal center
Fz
high forehead
Cz
central vertex/midline
A
auditory
what does electrocohleography (ECochG) measure
cochlear potentials
process of ECochG
sound (stimulus) is played through insert earphones, headphones, a speaker or bone ossilator, voltages are measured, EEG are averaged, remaining waves measured in relation to times based on start of stimulus
what are the two cochlear potentials
cochlear microphonic (CM) and summating potential (SP)
auditory brainstem response
another test that involves the CANS
-measures absolute latency, interpeak latency, amplitudes/amplitude ration, and neural generators
-playing a sound and measuring voltage changes
