6 AuditoryVestibular Flashcards by Jake Evans

Does CN VIII only have afferent nerve fibers?

no–efferent too

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What muscle attaches to the malleus and what nerve is it innervated by?

tensor tympani—CNV3

[Supression of self generated noise]

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What muscle attaches to the stapes? What nerve innervates?

stapedius—VII [dampens sensitivity to large sounds]

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What does damage to VII do to sound?

eliminates control resulting in extreme sensitivity (hyperacusis)

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T-F— the tonotopic arrangement of the basilar membrane is maintained throughout the auditory system?

true

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Excessive production of endolymph leads to what?

meniere’s disease

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Are outer hair cells or inner hair cells more sensitive to damage from extreme loud sounds?

Outer

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95% of the spinal ganglion cells are what type of nerve cell?

Type I that innervate inner hair cells.

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The cochlear nerve emerges from the internal acoustic meatus and enters brain near what? Terminating where?

pontomedullary junction

- dorsal and ventral cochlear nuclei

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What 2nd order neurons are thought to be involved in the acoustic startle reflex?

cochlear root neurons

[send axons to pontine reticular formation which then send them to spinal cord]

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What are the cochlear efferent fibers called? where do they begin? terminate?

olivocochlear bundle
superior olivary complex in pons
cochlear hair cells

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Do crossed olivocochlear bundle fibers innervate outer or inner hair cells?

Outer (majority)

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What is seen in patients with pontine strokes?

increased acoustic startle responses

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What symptoms are found in patients with cochlear nerve problems?

tinnitus and unilateral deafness

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What are two examples of cochlear nerve problems?

acoustic neuroma

- meningioma of the cerebellopontine angle

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Is the dorsal and ventral cochlear nuclei located lateral or medial to the inferior cerebellar peduncle?

Lateral in the floor of the 4th ventricle

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What is the path of axons leaving the dorsal cochlear nucleus?

cross midline at dorsal acoustic striae—–> ascend in the contralateral lateral lemniscus—->terminate in contralateral inferior colliculus

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Where do the majority of axons from the ventral cochlear nucleus end?

bilaterally in the periolivary nuclei of the superior olivary complex

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What are the 4 groups of the superior olivary complex?

medial superior olive
lateral superior olive
nucleus of the trapezoid body
periolivary nuclei

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What function is distinct to the medial superior olive?

binaural ability to localize sound due to TIME OF ARRIVAL

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What is the distinct function of the lateral superior olive?

binaural ability to localize sound due to INTENSITY CUES

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output of medial superior olive is carried in lateral lemniscus to where?

ipsilateral inferior colliculus

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what is the source of efferent olivocochlear bundle?

periolivary nuclei

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Lesions of the lateral lemniscus and inferior colliculus result in what?

only diminution of hearing in the ear contralateral to the lesion

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Lateral lemniscus carries information from what to what?

pontomedullary auditory nuclei to the inferior colliculus

Where does lateral lemniscus run in relation to the medial lemniscus?

dorsal and laterally

T-F--- lateral lemniscus is greatly affected by strokes because of a weak blood supply?

False---the opposite is true (rich blood supply less stroke damage)

What is the main output of the inferior colliculus?

inferior quadrigeminal brachium to the ipsilateral medial geniculate body

T-F---inferior colliculus has a binaural tonotopic organization arranged in laminae?

True

The thalamic relays for auditory information are located where?

medial geniculate body

What part of the medial geniculate body receives inputs from inferior colliclus and is tonotopically organized?

ventral nucleus

Where does the ventral nucleus of the medial geniculate body project to?

acoustic and auditory radiations----> primary auditory cortex

Where is the auditory cortex located in humans?

superior surface of the temporal lobe buried deep in the lateral sylvian fissure [note: there is much anatomical variation between right and left}

Where is primary auditory cortex found?

transverse temporal gyrus (heschl's)

What possesses a complete map of auditory frequencies?

primary auditory cortex

What happens in damage to primary auditory cortex?

loss of any awareness of sound, but reflexes involving sound are maintained

What area surrounds the primary auditory cortex? where do projections go?

belt auditory cortex---some projections go to Wernicke's area

T-F---all cortical auditory areas send axons back to the medial geniculate body, to the inferior colliculus and to the auditory cortex of the opposite hemisphere?

True

Where are the majority of disturbances in auditory function generated?

peripheral structures of inner ear, middle ear and cochlear nerve

Unilateral central lesions produce what changes in hearings?

subtle changes contralateral to lesion

bilateral strokes of temporal lobes affect what? what do they generally not affect?

- loss of ability to interpret speech | - sound sensitivity and ability to localize sound are less affected

what type of seizure accompanies auditory hallucinations and tinnitus?

temporal lobe seizures

what is the primary function of the lateral vestibule spinal tract?

maintain upright and balanced posture in response to both static and kinetic labyrinths

T-F---all cortical auditory areas send axons back to the medial geniculate body, to the inferior colliculus and to the auditory cortex of the opposite hemisphere?

True

Where are the majority of disturbances in auditory function generated?

peripheral structures of inner ear, middle ear and cochlear nerve

Unilateral central lesions produce what changes in hearings?

subtle changes contralateral to lesion

What are the clinical signs of damage to the vestibular system?

``` VANN vertigo ataxia nystagmus nausea ```

what type of seizure accompanies auditory hallucinations and tinnitus?

temporal lobe seizures

what are otoliths made of?

calcium carbonate crystals

T-F--the kinetic labyrinth is bilateral symmetrical?

True

When the head experiences angular acceleration, what happens to the endolymph?

it lags behind due to inertia and deflect the cupula

If excitation occurs in afferent neurons of one semicircular canal, what happens to the the opposing canal of the opposite semicircular duct?

causes inhibition of those afferents [push-pull operational mode]

Where do axons from vestibular nerve synapse?

vestibular nuclear complex

IS there an efferent part of the vestibular nerve?

yes-axons come from vicinity of the vestibular nuclear complex and help with signal processing

Where is the second order component of the vestibular pathway located?

dorsally in the pons and medulla between lateral part of the 4th ventricle and the inferior cerebellar peduncle

what are the 4 main vestibular nuclei?

lateral vestibular nuclei medial superior inferior

can all 4 main vestibular nuclei be seen in same cross section?

No---they are present in a considerable rostral caudal distance from the rostral medulla to middle pons

Where are the main outputs of the vestibular nuclei to?

- spinal cord - oculomoter - cerebellum - minor outputs to thalamus to parietal cortex

What is vestibular information used for?

eye position, neck position, limb/body position reflexes

What is the name of the reflex system for the the neck and vestibular system?

vestibular-collic reflex | [V-spinal and V-ocular for other reflexes]

Damage to anterior cerebellar lobe and flocculonodular lobe leads to what clinical signs?

similar to those found after damage to the vestibular system

What is the main function of the medial vestibule-spinal tract?

- -adjust position of the head in response to change in posture - - integrates head and eye movements via superior projections of MLF

Do MLF fibers directly or indirectly innervate CN III and CN VI?

indirectly

Does the medial or lateral vestibular tract arise from fibers from their respective nucleus on both sides?

medial does, lateral does not

Activation of the lateral vestibular tract leads to what?

activation of axial extensors and inhibition of axial and appendicular flexors

what is the primary function of the lateral vestibule spinal tract?

maintain upright and balanced posture in response to both static and kinetic labyrinths

How many neurons are in the VOR arch?

3, primary afferent, vestibular nuclear neuron, and the oculomotor neuron

In the VOR…what nucleus send excitatory fibers and which sends inhibitory fibers

medial vestibular nucleus = excitatory superior vestibular nucleus= inhibitory

What connects to the superior vestibular nucleus and inhibits the vestibuloocular reflex?

flocculus- permits smooth pursuit

Presence or absence of the VOR can be used in comatose patients to determine what?

if the brainstem is intact----doll head maneuver

What are the clinical signs of damage to the vestibular system?

``` VANN vertigo ataxia nystagmus nausea ```

does meneire's labrynthitis, and alcohol intoxication affect central connections?

No--peripheral

Does dorsal medullary syndrome, affect the central connections of the vestibular system?

Yes