the vestibular system Flashcards
(15 cards)
What is the point of the vestibular system
-Answers two basic questions:
=‘Which way is up?’
=‘Where am I going?’
-Contributes to:
=Keeping our eyes still as we move
=Maintaining our upright posture
=Our ability to perceive our own movement within space
whats the Gross anatomy of the vestibular system
-ampulla:
=where most canals have expansions
=where the hair cells are found
-vestiblar nerves
-sensory receptors :
= semicircular canals (head rotations)= anterior vertical, posterior vertical, and horizontal (all 90 degrees from one another)
=otolith organs (linear motion) = ultricle (detects things in horizontal plane) and saccule (detects things in the vertical plane)
what is the The vestibular labyrinth filled with
-endolymph
-which has high K+
what are the The primary sensory receptors of the vestibular system
-hair cells
what do vestibular hair cells have
-a hair bundle with stereocilia and tip links
-a kinocilium throughout life
-has stereostibular and hair bundles- they have kinocillium which defines polarity of cell (direction of staircase)
-more rows and not as high spread
-good for detecting low frequencies
what are vestibular hair cells
-mechanosensitive
-Same principle as hair cells of the auditory system but they respond to lower frequencies
-resting discharge exists because channels are open a little bit which leads to a little bit of resting tension-high K+ leads to depolarisation due to the stretching which opens up the channels
what are the two types of vestibular hair cell
-both one information to the vestibular part of the brain cell- just have different properties of how they communicate with afferent fibre
-type I and II
-type I= reliable transmission due to NT release along base of the cell as it activates afferent terminal, involving the calyx (longer a=with a bigger dome)
what do the saccule and the utricle detect
-head tilt and linear acceleration
-saccule= up or down direction of your head
-utricle= left to right direction
-there is Otoconia on top of the Gelatinousotolithic membrane
-on top of Otoconia there is calcium carbonate structures and gravity pulls on this pulling the membrane down
-Striola- one side= hair cells are orientated in one direction, the same for the other side
-Hair cells are found in a sensory patch called the macula
-Hair cells depolarise, exciting fibres
-Hair cells hyperpolarise, fibres are quiet
why can Vestibular input to the CNS can be ambiguous
-activated when stepping to your right
-otilic membrane ,oves slower because its heavier
-moves slower than the rest of the vestibular system
-2 movements are activating some cells and afferent fibres
-input from visual fields
whats the Anatomy of the ampulla of the semicircular canals
-The cupula (softer) have hair cells which the cell bodies are sat at the bottom of the ampulla and protect up to the cupulla is a gelatinous structure penetrated by hair bundles
-endolymph always around hair bundles
how can the The semicircular canals detect angular acceleration (rotation)
-endolymph in semicircle canals move but not necessarily with your body
-The inertia of endolymph during rotation displaces the cupula
-endolymp keeps moving in direction that you were spinning in, that’s why when you stop it feels like you’re still moving
why do Semicircular canals on either side of the head work in pairs
-Horizontal canals on both sides lie in roughly the same plane so can act as a functional pair.
-The anterior canal on one side lies in parallel with the posterior canal on the other side so acts as a functional pair
whats the The vestibular nerve and central pathways
-Vestibular organs (semicircular canals & otolith organs) -> Cerebellum -> Vestibular nuclei -> Cerebral cortex -> Spinal cord -> Reticular formation -> Oculomotor nuclei (only this one) -> Extraocular muscles
-look at slide 16
what is the The vestibulo-ocular reflex
-when shaking your head you have vestibular input+ visual
-when shaking the paper you only have visual system
what does Vestibular nystagmus enable
-the resetting of eye position during sustained head rotation
-Experiment: subject seated and rotated towards the right at a constant rate in the dark
-Slow phase: Eyes rotate in the opposite direction to head movement
-Quick phase: Rapid resetting movement back to the centre of the gaze
-Right quick phase movement = right beating nystagmus
