Auditory and Vestibular Systems Flashcards by Kelsy Schoen

Term: Sense of sound

Audition

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Describe the stimulus for the auditory system

Pressurized sound waves of varying frequencies

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Structure: From the pinna to the tympanic membrane

Outer ear

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Structure: From the tympanic membrane through the stapes

Middle ear

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Structure: Past the stapes and containng the cochlea

Inner ear

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3 Middle ear bones

Malleus
Incus
Stapes

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Describe the movement of sound waves through the auditory system

Pinna collects sound wave

Sound funneled through external auditory canal

Vibrates tympanic membrane, inner ear bones, oval window

Vibrates fluid in cochlea

Fluid moves and stimulates hair cells

Responses picked up by cochlear nerve

Travels to the cortex

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Structure: Contains receptors that recieve sound

Organ of Corti

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Describe the function of the partition between the perilymph and enodlymph of the cochlea

The parition forces fluid to move in one direction allowing for continuous sound reception

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Describe the structure of the organ of corti

3 outter hair cells are attached to the inner hair cells. The outer hair cells fine tune the inner hair cell which transmits sound

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Describe the function of the tectorial membrane

The tectorial membrane is pushed down by the fluid in the cochlea to stimulate the hair cells within the organ of corti

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Describe how a hair cell is depolarized

Hair cells have cilia attached by tipplings. The direction of cilia movement determines if the signal is inhibitory or excitatory. As the cilia move/vibrate the tipplings are pulled opening K+ channels. Opening of the K+ channels depolarizes the hair cells letting Ca+ rush in. Neurotransmitters in vesicles then move to the membrane and are released stimulating the postsynaptic cell

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Describe the arrangement of sound reception within the cochlea

Tonotopic arrangement

higher frequencies at the base
lower frequencies at the apex

ALL frequencies DO NOT stimulate every single hair cells.

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3 functions of the auditory system in the CNS

Activating effect of sound (will wake you up)
Orienting effect (will move head and eyes to sound)
Recognition of sound

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Pathway: Connection to auditory system increases awareness

Reticular formation

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Pathway: Connection to auditory system processes information from both ears allows you to determine where the sound is coming from

Inferior colliculus

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Pathway: Connection to the auditory system moves your head and eyes toward sound

Superior colliculus

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Pathway: Connection to the auditory system that relays information to the primary auditory cortex

Medial geniculate body

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Cortical area: Comprehension of sound

Wernicke’s area

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Condition: middle ear bones don’t move well, would NOT benefit from a cochlear implant

Otosclerosis

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Condition: Common in children, middle ear infection

Otitis media

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Condition: Hearing sound without stimulus to the auditory system

Tinnitus

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Condition: Loss of hearing due to pressure on the nerves, may be due to a benign tumor

Acoustic Neruoma

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How would you discriminate between and inner ear condition and a cochlear condition?

Use of tuning fork and place it on the mastoid process

Can hear = middle ear problem

Can’t hear = cochlear problem

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Describe the cause of age related hearing loss

There is a loss of hair cells/receptors

Acronymn: BPPV

Benign Paroxysmal Positional Vertigo

Top 3 complains to PCP

1. Chest pain 2. Fatigue 3. Dizziness

3 Systems that work together for Balance

1. Vestibular 2. Vision 3. Somatosensory

Location: Vestibular 1. Peripheral sensory appartatus 2. Central processing system 3. Motor system

1. Inner ear 2. Vestibular nuclei in brainstem 3. Ocular/Skeletal muscle

Structure: Provides sensory input about both agnulgar and linear acceleration

(Vestibular) peripheral sensory apparatus

Structure: Oreitns the head with respect to gravity

(Vestibular) peripheral sensory apparatus

Structure: Somatosensory and visual cues with connections to the reticular formation, cortex, and direction connections to the cerebellum

(Vestibular) Central processing system

Describe the structure of the vestibular peripheral sensory apparatus

Consists of 3 semi-circular canals containing fluid and lined with hair cells. Stimulation of this system gives you information about the position of your head

2 Vestibular peripheral sensory apparatus structures that detect linear movement/acceleration and gravity

Utricle and Saccule

3 Vestibular peripheral sensory apparatus structures that detect angular movement (yaw, pitch, roll)

Anterior, Posterior, Lateral Semi-Circular Canal

Describe the push pull system within the vestibular peripheral sensory apparatus

Relates to the peripheral sensory apparatus working in tandem to make the system more sensitive Ex. When you turn your head to the right, the right horizontal canal is stimulated and the left horizontal canal is inhibited Ex. Bending down right anterior is stimulated and left posterior is inhibited. The same is turn for the left anterior/right posterior relationship

Describe how hair cells in the vestibular peripheral sensory apparatus are 1. Stimulated 2. Inhibitied

1. Fluid moves toward the hair cell 2. Fluid moves away from the hair cell

Term: Rotation

Yaw

Term: Up and down

Pitch

Term: Side bend

Roll

Describe how the horizontal canal is oriented

It sits at 30 degrees

Structure: Biological sensor which converts head motion to neural firing present in the ampulla and otolith organs

Hair cell

Describe the "window" into the vestibular system

The eyes, each canal has its own unique eye movement

2 Otolith organs and their orientation

1. Utricle - horizontal plane (stimulated with sideways motion) 2. Saccule - vertical plane (stimulated with up/down movement)

Purpuse of the information from otolith organs

Balance control

Describe the macula and the purpose of otoconia

Hair cells covered by a gelatinous substance with otoconia on top The otoconia are senstive to gravity, get sheared along the gel with movement and that information is transferred to the hair cells in BPPV the otoconia are disloged and moved to the semicircular canals disrupting the flow of fluid

2 Structures that provide information to postural muscles

Utricle and saccule

Structures for maintaining a stable gaze

Semicircular canals

2 Functions of the Vestibular system

1. Maintain steady gaze 2. Postural balance

Describe the firing rate of the central processing system at rest and with movement

There is a baseline firing rate that is symmetrical at rest With movement the stimulated side increases its firing rate while the inhibited side decreases its firing rate resulting in balanced input to the CNS

Central Vestibular System: Describe the function of the following structures 1. Flocculondular lob of cerebellum 2. Inferior/Superior Vestibular Nuclei 3. Vestibulospinal tracts 4. Vestibulocolic pathways 5. Vestibuloautonomic pathways

1. move eye amount needed to maintain gaze 2. MLF, CN III, IV, VI 3. UE/head position 4. Innervate the trap/SCM, turn/right the head 5. Sweat/throw up

Defn: Vestibulo-ocular reflex

Stabilizes eyes when head moves

Defn: Vestibulo-spinal reflex

Balance control

Tract: Connection between vestibular system and stability muscles of the torso and LE (below neck)

Lateral vestibulospinal tract

Tract: Head position

Medial vestibulospinal tract

Reflex: Large perceptive field, slower to activate

Otokinetic reflex

Condition: Results from a deficit in the vestibulo-ocular relfex causing unmaintained gaze while walking/running/etc.

Oscillopsia

Defn: VOR Gain

As the head moves in one direction the eyes moves in the opposite direction with equal velocity VOR Gain = Eye velocity/head velocity 1 is normal

Describe the system responsible for maintaining gaze stability at \> 60 deg/sec

Vestibular

Describe the system responsible for maintaining gaze stability at \< 60 deg/sec

CNS - smooth pursuit

Condition: Difference between sides in the tonic firing rate within the vestibular nuclei

Nystagmus

Term: More than 1 or 2 movements to look from point A to point B

Saccades

Describe how a disruption in th vestibular system manifests via eye movement

The eye movement that would indicate a vestibular problem would be saccades

Describe the direction of the saccade in relationship to the affected side

Nystagmus is named for the direction of the eye movement The slow phase is driven by the ears while the fast phase is driven by the CNS If the the lesion is defict causing, the nystamus will beat to the opposite side or AWAY from the lesion If the lesion is irritative the nystamus will beat to the same side or TOWARD the lesion

7 Non-vestibular causes of dizziness

1. Disuse equilibrium 2. Orthostatic hypotension 3. TIA 4. Panic attacks 5. Migraines 6. Diabetes 7. Concussions

Condition: - Usually unilateral - Sx with change of head position - Debris in inner ear

BPPV

Disrupted canal that matches the following nystagmus 1. Horizontal 2. Upbeats with torsion

1. Lateral semi-circular canal 2. Posterior semi-circular canal

Condition: Acute inflammation of the vestibular nerve

Vestibular neuritis

Condition: Bacterial infection of the labrinth causing hearing loss

Vestibular labyrinthitis

Condition: Separation of the middle ear from the inne ear typically as a result of head trauma, penetrating injury, or vigorous straining

Perilymphatic fistula

Condition - 40-60 yo - Malabsorption of endolymph - Hearing loss and vertigo - Attack resolves in 48-72 hours

Meniere's Disease

Condition: Severe balance loss without accompanying dizziness due to ototoxicity

Bilateral vestibular loss

Describe the appearance of central nystagmus

Unlike peripheral nystagmus which will have a consistent direction/beat, central nystagmus will have no pattern/keep changing directions

Condition: The sensation you're still moving after spending extended time on a boat

Mal de Debarquement Syndrome

Describe the catch 22 with vertigo medications

Most suppress the vestibular system with can affect your balance while helping your dizziness