L24 The Vestibular System (Imported from Quizlet)

Which way is up? and where am I going?

What 2 questions does the vestibular system answer?

Keeping our eyes still as we move, maintaining our upright posture, our ability to perceive our own movement within space

What does the vestibular system contribute to?

Inner

Which part of the ear is the vestibular system?

Semicircular canals and otolith organs

What are the 2 main anatomical structures of the vestibular system?

Head rotation

What do semicircular canals detect?

Anterior vertical, posterior vertical and horizontal - all for different types of rotation

What are the different types of semicircular canal and what do they do?

Wide openings called ampulla

What is at the ends of the semicircular canals (where mechanotransduction machinery is found, hair cells)

Linear motion

What do otolith organs detect?

Utricle and saccule

What are the 2 parts of the otolith organs?

Movement up and down

What does the saccule detect?

Movement forward and backwards

What does the utricle detect?

Endolymph

What are the utricle and saccule filled with?

Endolymph, perilymph

In the semicircular canals, the middle bit is filled with ____________ and the chambers either side are filled with ___________

Sensory receptors of the vestibular system

What are hair cells?

Lower, 0, 20

Hair cells of the vestibular system have the same principle as hair cells of the auditory system but they respond to ________ frequencies (_ to ~__Hz)

Stereocilia, hair bundle

Each individual strand is a _____________ but the entire structure that sits on top of hair cells is known as _____ __________

Upright

If there's no stimulus/movement then the hair bundle stands ___________

Tip links are stretched, MET channels open and potassium moves in causing graded potential from the top to the base (depolarisation) causing voltage-gated calcium channels to open and calcium comes in and this causes release of glutamate which activates glutamate receptors in the afferent fibres of the vestibular system and general EPSPs and this can stimulate to become action potentials if the EPSPs are big enough

What happens if the hair bundle moves towards the taller stereo cilia?

Tip links become slackened, the channels shut, potassium cannot come in so the hair cell will hyperpolarise, decreasing in frequency of nerve impulses

If the hair cells are moved towards the shorter stereo cilia, what happens?

Tension

Both in the auditory and vestibular system there is some _________ on the hair cell at rest

Kinocilium

What do vestibular hair cells keep throughout life that cochlear hair cells don't?

Clumpy, rows, lower

Vestibular hair cells are more _______ but retain the staircase structure but have more _______ - this is due to the _________ frequencies stimulating it

3

How many rows of stereo cilia do cochlear hair cells have?

Type I and Type II

What are the two types of vestibular hair cells?

How they communicate with the afferent fibre

What is the major difference between Type I and Type II hair cells?

Typical neurone to neurone contact

What communication with the afferent fibre do Type II hair cells have?

Calyx

In Type I there is a massive __________ which is a postsynaptic region massively expanded to enclose the bottom of the Type I hair cell

Head tilt, linear acceleration

The saccule and the utricle detect ______ _______ and _________ ______________

Macula

Hair cells are found in a sensory patch called the ...?

Striola, opposite

Inside the macula there is a wobbly line known as the ________ where on one side hair cells are orientated in one direction (taller hair cells pointed towards it) and on the other side the hair cells are the ___________ way

Gives a dual response - as one is activated the other is inhibited

What does the orientation of the hair cells within the macula do?

Jelly, calcium crystals

Otolithic membrane is ______ like and otoconia are ___________ __________

Gravity, hair cells

If you move, the otoconia moves due to _________ and pulls the otolithic membrane which in turn pulls the ______ _______ with it

All the CNS is hearing is that the nerve fibres have been activated but it does not know how it has been activated

Vestibular input to the CNS can be ambiguous, why?

Endolymph, otoconia

______________ and ___________ are heavier, they won't move as quickly as the rest of the body so they drag the hair bundles in that direction

Force of gravity

What does Fg stand for?

Cupula

What is the name of the gelatinous structure penetrated by hair bundles?

It forces them to move

If the cupula moves, what happens to the hair bundles?

Angular acceleration

The semicircular canals detect _________ _____________ (rotation)

Inertia, displaces

The _________ of endolymph during rotation __________ the cupula

Pushing, right, hair bundles

Endolymph takes a while to move so even though you rotate to the left the endolymph won't catch up, so because of that if you move it appears the endolymph is turning to the right therefore __________ the cupula to the _______ and with it the ______ __________

Pairs

Semicircular canals on either side of the head work in ...?

Right, activation, inhibition

As we turn to the left, the endolymph turns to the _______ in both semicircular canals, this causes _____________ on one side of the head and _____________ on the other side due to the rotation of the hair bundles

Same plane, functional pair

Horizontal canals on both sides lie in roughly the ______ _______ so can act as a _____________ ______

Parallel, functional pair

The anterior canal on one side lies in __________ with the posterior canal on the other side so acts as a _______________ ______

Vestibular nuclei (in the brain stem)

Where is the first place the vestibular organs input into?

Perception

What does the cerebral cortex allow?

Sends information to the muscles of the eye (ocular = eye, motor = muscles) - adjusts the eye muscles

What does the oculomotor nuclei do?

Change in movement

What does the spinal cord allow?

Motor coordination

What is the cerebellum important in?

Cerebellum

The vestibular system needs a strong link to the ...?

Brain stem, oculomotor nucleus, abducens nucleus

When shaking your head you activate your vestibular system and hair cells, allows communication into ________ _______ and allows connection with _______________ _________ and ____________ __________ which pulls your eyes back in the right direction

Pull your eyes to the right

If you move your head to the left and you want to remain focused, what must your eye muscles on your right do?

The resetting of eye position during sustained head rotation

What does vestibular nystagmus enable?

Eyes rotate in the opposite direction to head movement

What is slow phase?

Rapid resetting movement back to the centre of the gaze

What is quick phase?

Right beating nystagmus

Right quick phase movement = ?