Vestibular System Flashcards by Sarah Anderson

What is the overall function of the Vestibular system

Posture and balance

How well did you know this?

Not at all

Perfectly

Where is the vestibular system located

In the inner ear, embedded in the temporal bone

How well did you know this?

Not at all

Perfectly

What is the vestibular system composed of

series of fluid filled membraneous tubes = labyrinths

How well did you know this?

Not at all

Perfectly

What is the apparatus of the vestibular system

3 semi circular canals
Utricle
Saccule

How well did you know this?

Not at all

Perfectly

What is the position of the semi circular canals

Are three dimensional due to being all right angled to each other

How well did you know this?

Not at all

Perfectly

What is the swelling at the base of each semicircular canal called

Ampulla

How well did you know this?

Not at all

Perfectly

Where is the utricle located

Swelling at the base of all the semicircular canals connecting them all

How well did you know this?

Not at all

Perfectly

Where is the saccule located

The swelling underneath the base of the utricle

How well did you know this?

Not at all

Perfectly

Where is sensory hair cells located in the vestibular apparatus

The ampulla of semicircular canals
Saccule
Utricle

How well did you know this?

Not at all

Perfectly

What is the collective name of the utricle and the saccule

Otolith organs

How well did you know this?

Not at all

Perfectly

What is the overall function of the otolith organs utricle

Detects linear acceleration and encode the position of the head in space

How well did you know this?

Not at all

Perfectly

What is the overall function of the otolith organs saccule

detects vertical movement

How well did you know this?

Not at all

Perfectly

What is the overall function of the semicircular canals

Detects rotational acceleration

How well did you know this?

Not at all

Perfectly

Where are the sensory cells of the semicircular canals embedded

The ampulla

How well did you know this?

Not at all

Perfectly

What is the sensory receptors called inside the ampulla

Cristae

How well did you know this?

Not at all

Perfectly

What does the cristae consist of

A cupula - a flexible gelatinous strucutre

How well did you know this?

Not at all

Perfectly

How is the crisate arranged in the ampulla

Stretches over the width of the ampulla

How well did you know this?

Not at all

Perfectly

What is further embed in the cupula of the ampulla

Cilia of hair cells, which act as receptor cells

How well did you know this?

Not at all

Perfectly

What is the purpose of the cilia of hair cells in the cristae

Synapse directly with the sensory neurones of the vestibular nerve

How well did you know this?

Not at all

Perfectly

How is the cilla of hair cells receptors activated

By the movement of the endolmlyph in the semicircular canal pushing the gelatinous cupola of the cristae

How well did you know this?

Not at all

Perfectly

What moves first when rotation of the skull occurs

The ampulla

How well did you know this?

Not at all

Perfectly

Why doesn’t the endolymph move at first on rotation

As isn’t embedded in the skull

How well did you know this?

Not at all

Perfectly

How does the hair cells in the Cupula detect rotational acceleration

Due to the inertia of the endolymph producing a drag which bends the cupula in the opposite direction of rotational movement and overall activates the cilla

How well did you know this?

Not at all

Perfectly

What cause the endolymph to catch up the the rotational speed

Rotating at a constant velocity for several seconds

How well did you know this?

Not at all

Perfectly

What is the affect of the endolymph catching up with the rotational speed

Endolymph now rotating at the same velocity so remove the sheering force, and cuppa no longer distorted

How does dizziness occur if you suddenly stop high velocity rotation

endolymph to continue to move due to momentum creating a continuing sense of movement

What is the two types of cilia hair cells

Kinocillium - single very large | Stereocillia - smaller series

What does distortion of the cilla in the direction of the Kinocillium cause

Depolarisation and increase discharge of the APs in the vestibular nerve

What does distortion of the cilia away from the Kinocillium lead to

Hyperpolorisation and decrease discharge of APs in the vestibular nerve

What does movement of the kinocillium allows the brain to determine

Movement in time and space

Why is the orientation of the cupula all slightly different

So the brain can build a 3D image of body position using the pattern of firing and inhibition received.

Where does the integration of the sensory information from vestibular apparatus take place

The cerebellum

When you stop rotating after rotating at constant velocity, what happens to the movement of endolymph and the cupola

The endolymph continue to move die to momentum But the sheering of the cupula is in the opposite direction that at the start

What is the name of the sensory receptors in the otolith organs

Maculae

How is the Maculae orientated in the utricle

In the horizontal plane

How is the Maculae orientated in the saccule

In the vertical plane

What is the structure of the maculae

Set of cilla which embed into the gelatinous mass called the otolith membrane

What is embedded into the otolith membrane

CaCO3 crystals called otoliths.

What affect the positioning of otolith crystals

Gravitational forces

What doesn't have much input on the positioning of the otolith crystals, why?

Endolymph | as otoliths have greater density

How do the macule in the utricle detect the tilting of you head

Tilting the head moves the otoliths and the otolith membrane in which they are embedded. This distorts the jelly, and moves the cilia

What head tilt moves the otoliths in the direction of the kinocillium resulting in depolarisation

Backward tilt

What occurs when the head it tilted forward

Otoliths move in the opposing direction of the kinocillium resulting in hyperpolorisation decreasing AP discharge

What do the vertically orientated macule in the saccule respond to

Vertical forces e.g. movement in a lift

What provides information of the orientation of the head when lying down

The macula in the saccule

Where does the information to the brain via the vestibular nerve all originate from

The three cristae of the semicircular canals | and the two macule of the otolith organs

Where does many sensory afferents of the vestibule nerve terminate

In the vestibular centres in the medulla

How does the cerebellar centres associate with the vestibular centres

By co-ordinating the postural muscles required to maintain balance

Where does vestibular nuclei receive input from

Proprioceptors signalling limb and body position, Neck, Eye muscles

What is the vestibular nuclei

cranial nuclei for the vestibular nerve

Where is the vestibular nuclei found

grouped in both the pons and the medulla in the brainstem

How and where do the projections from the vestibular nuclei project

Project ipsilaterally, bilaterally and contra-laterally to descending motor pathways and the extra ocular nuclei/muscles

How does vestibular nuclei project to the cerebral cortex

Via the thalamus

What does the vestibular nuclei project to the cerebral cortex

perception of movement and body position = kinaesthesia.

Name three vestibular system reflexes

Tonic labyrinthine reflex Dynamic righting reflex Vestibulo-occular relflex

What does the vestibule system reflexs involve

Vestibulocortical and vestibulospinal tracts

What occurs in the tonic labyrinthine reflex and how does it happen?

The axis of the head is kept in a constant relationship with the rest of the body. Use information from maculae and neck proprioceptors

What occurs in the dynamic righting reflex and how does it happen?

Rapid postural adjustments that are made to stop you falling when you trip. Long reflexes, involving extension of all limbs

How does vestibular apparatus have a strong connection to visual apparatus

Afferents from the semi-circular canals project and connect (within the vestibular nuclei) to afferent fibres travelling to the extraocular nuclei and thus have strong input to influencing eye movement.

What demonstrates the strong association between visual system and postural control

An increased difficulty experienced with balance when you close your eyes

How do people with vestibular apparatus destruction maintain good balance and how do they loose balance

Balance is good if movement is relatively slow and eyes are open Balance is lost if they close their eyes

What is the two vestibulo-ocular reflex

Static reflex | Dyanmic vestibular nystagmus

What occurs in the static reflex

When you tilt your head, the eyes intort/extort to compensate, so that over a certain range, the image stays the right way up

What occurs in the dynamic vestibular nystagmus

series of saccadic eye movements that rotate the eye against the direction of rotation of the head and body so that the original direction of gaze is preserved despite head rotating

What occurs when the eyeball comes to the end of its range of movement

The extent of eye movement is restricted so it rapidly flicks back (nystagmus) to looking straight ahead

Define nystagmus

Rapid involuntary movement of the eye

If the head is rotating right what is the direction of the nystagmus

Right

In Post rotary nystagmus (at the end of rotation and nystagmus has occurred in the direction of the rotation) Why then do you then get nystagmus in the opposing direction

As In the deceleration the endolymph is catching up and now pushing the cupula in the opposite direction

How in caloric stimulation when the ear is washed with either cold or warm fluid is the vestibular system stimulated

As fluid gets through the thin bones and sets up convection current affecting the endolymph

What is the affect of warm fluid >37C

Sets up nystagmus towards the affected side

What is the affect of cold fluid <37C

sets up nystagmus away from the affected side

What are the two tests that check vestibular function by investigating nystagmus s

Caloric stimualtion (ear washed with water) Post rotary nystagmus (rotated in a chair)

What is the symptoms experienced due to caloric stimulation

Nausea | Vomiting

Why is it good to test fro nystagmus

As shows if any lesions are present in the periphery to central vestibular pathways

Powerful maintained stimulation of the vestibular system can cause what

Kinetosis - motor sickness

Why does motion sickness/kinestosis occur in moving vehicles

Visual and vestibular system inputs to the cerebellum are in conflict

How does the cerebellum generate the symptoms of motion sickness

sends“sickness signal” to the hypothalamus to bring about the autonomic changes

What is the autonomic nervous symptoms caused by motion sickness

``` Nausea Vomiting decreased blood pressure Dizziness Sweating Pallor ``` = all equal autonomic

What symptoms does acute infection of vestibular apparatus - labyrinthitis

Autonomic Nervous system symptoms Vertigo

what is the symptoms of Mieinieres disease

Vertigo Nausea Nystamgus Tinnuitis

How does menieres disease affect vestibular function

as associated with overproduction of endolymph

What drugs is the inner ear sensitive towards

Streptomycin

How does a lesion of the brain stem affect vestibular function

Can cause nystagmus at rest