Central Auditory Pathways (ascending/descending/reflexive) Flashcards

1
Q

what are the central auditory pathways (3)

A

1) ascending
2) descending
3) collateral

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2
Q

incoming sensory signals

A

ascending

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3
Q

feedback mechanisms to reduce unwanted noise & focus attention

A

descending

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4
Q

CN reflexes
learned orientation reflexes

A

collateral

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5
Q

all structures are __________________ in the ascending auditory pathway

A

tonotopically organized

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6
Q

where does tonotopicity exist?

A

at all levels & within nuclei and fiber bundles (pathways)

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7
Q

afferents from most sites project _____ (MGN is the exception)

A

bilaterally

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8
Q

3 sites of obligatory synapse

A

1) cochlear nucleus
2) MGN of thalamus
3) auditory cortex

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9
Q

auditory fibers enter the central pathway via CCN VIII at the __________________

A

cerebellopointine angle; which is the boundary between medulla & pons

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10
Q

identify the IC and MGN of the thalamus

A
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11
Q

MGN only projects to _____________ primary auditory cortex

A

ipsilateral

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12
Q

______ are the first-order neurons of the central auditory pathways

A

spiral ganglion neurons (SGN)

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13
Q

Type I SGN

A

90-95%
large true bipolar
more myelinated
metabolically active
peripheral process: go to one IHC (10-20 contacts)

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14
Q

Type II SGN

A

unipolar
peripheral cross tunnel of Corti to branch and innervate 10-15 OHC

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15
Q

what does the organ of corti look like

A
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16
Q

mainly myelinate axons from Type I
uniform myelination –> signal transmission synchronization (CAP - which is a physio measure of nerve activity)
apex : low / basal : high
all fibers synapse –> bifurcate and send to collateral branches (AVCN/PCVN/DCN of nuclear nucleus)

A

cochlear nerve / auditory nerve

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17
Q

cochlear nucleus (AVCN, PVCN, DCN)

A

diverse projections such as other brainstem nuclei (dorsal middle/ventral acoustic stria - trapezoid body) and contralateral medial lemniscus and IC

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18
Q

________ is a site of obligatory synapse for all _____ fibers

A

cochlear nucleus

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19
Q

1) dorsal to contral lateral lemniscus
2) intermediate to contra lateral lemniscus and few to SOC
3) ventral (trapezoid body) to both ipsi and contra SOC

A

acoustic striae

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20
Q

superior olivary complex (SOC) subdivisions

A

1) medial superior olive
- receive ipsi & contra inputs
2) lateral superior olive
- localization of higher freq signals
3) MNTB
- input from contra CN and projects to ipsi SOC (enhance intensity and timing distinctions)
4) periolivary groups

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21
Q

SOC projections

A

axons from SOC ascend, along with fibers from contra CN

22
Q

axons from SOC ascend, along with fibers from contra CN, to form a pathway called _____________

A

lateral lemniscus

23
Q

pathway of fibers, which some synpase with neurons in nucleus of lateral lemniscus

A

lateral lemniscus (LL)

24
Q

receives all fibers from LL
some may pass through IC to SC
2nd, 3rd, 4th, or even higher order (neurons)
2nd order fibers from contra CN
projects to ipsi and contra MGN of thalamus

A

inferior colliculus (IC)

25
Q

thalamus is the sensory relay station for ________ sensory info headed to cerebral cortex

A

ALL

26
Q

what is the subdivision of the thalamus responsible for auditory signals

A

medial geniculate nucleus / medial geniculate body

27
Q

what is located on the superior surface of the TEMPORAL LOBE

A

primary auditory cortex

28
Q

primary auditory cortex lies predominately on ____________

A

Heschl’s

29
Q

higher frequencies are located more _______ and low frequencies more ______________ in the primary auditory cortex

A

posteriorly ; anteriorly

30
Q

the neuronal activity at any level, and thus the information extracted, may be modified by ___________ feedback circuits

A

descending

31
Q

OCB
feedback circuits with SOC, LL, IC to CN
contra CN to CN
cortex to lower

A

descending pathway

32
Q

allows ascending (efferent) control over cochlea

A

OCB

33
Q

OCB fibers run with CN VIII and arise from two populations of cells with SOC: 1) __________ and 2) ___________

A

LSO (small cells)
MSO (large cells)

34
Q

_______ is used as the neurotransmitter to hyperpolarize OHCS by opening K+ channel

A

ACh

35
Q

latency of response of synaptic activity of the OCB is ________ msec following the sound stimulus

A

10-30 msec

36
Q

the _____ nature of this system allows 1 cochlea to affect responses of the other cochlea

A

bilateral

37
Q

MOC activity decreases the active processes of OHCs (leading to freq-specific reduction of cochlear gain)
precise cochlear function (sharp tuning curves)
detection and discrimination of sounds in noise by suppression of continuous background noise

A

proposed functions of the OCB

38
Q

another name for the stapedial reflex, ME acoustic reflex, ME muscle reflex, attenuation reflex

A

acoustic reflex

39
Q

what does the acoustic reflex represent

A

true CN reflex with simple reflex arc

40
Q

stimulus threshold for the reflex averages around ______ dB but ranges from _______ dB

A

85 ; 70 -100 dB

41
Q

in humans, the reflex contracts ONLY the ________ muscle bilaterally

A

stapedius

42
Q

contralateral response is __________ and slightly ___________

A

slower and weaker

43
Q

what can the reflex help identify

A

(CN VII) facial nerve lesions or retrocochlear lesions
0 such as vestibular schwannoma

44
Q

why is it beneficial for the reflex to be activated in anticipation of the onset of vocalization?

A

it can reduce sound intensities reaching the ear by about 20 dB

45
Q

functions of the acoustic reflex (3)

A

1) protection from loud sounds
2) mostly dampens low freq sounds
- may inhibit masking of high freq by lower freq
3) possibly to reduce likelihood of our vocalizations interfering with normal hearing

46
Q

orientation reflex:
______________ generates and controls eye and head movements based on signals from different senses

A

superior colliculus

47
Q

orientation reflex:
some auditory fibers of the ____________ pass right through the IC to reach the superior colliculus

A

lateral lemniscus

48
Q

orientation reflex:
inputs integrated by SC directs extraocular muscles and spinal motor neurons to allow a learned __________ orientation

A

reflexive

49
Q

____________________ is highly synchronized, allowing the measurement of signal processing (neuronal activity) to be conducted, even non-invasively (ABR)

A

auditory signal transmission

50
Q

the ______________ of neural activity associated with auditory signals is unmatched by other neural networks or sensory systems

A

fidelity / precision