Neuro 11 - Vestibular Systems Flashcards
Where is the vestibular labyrinth located
Petrous temporal bone —> filled with perilymph
Describe the organelle structure of the vestibular labyrinth
- Saccule - connected to utricle and cochlea
- Utricle
- 3x semicircular canals. Posterior (/inferior) semicircular canal, anterior (/superior) semicircular canal and lateral semicircular canal. All canals meet at utricle
Vestibular hair cell cilia are embedded in?
Gelatinous matrix containing CaCO3 crystals - otoconia
Vestibular hair cells are mechanical transducers that detect static tilt and acceleration (i.e. if you move at constant speed, fluid doesn’t move, eyes don’t move). Describe their basic structure
Sensory hairs have stereo cilia - arranged in rows of varying highs, with a single long kinocilium
The nerve endings are 2 types:
Type 1 - chalice like endings forming ribbon synapses
Type 2 - simple nerve terminals
Briefly describe the transduction mechanism
(Similar to cochlea)
Hair cell receptor potential produced –> if hair cell moves towards kinocilium, depolarisation. If away then hyper polarisation
Ganglion cell discharge also depends on direction –> if toward kinocilium, increased frequency, if away from kinocilium, decreased frequency
What does the striola do?
and static labyrinth
Striola - divides hair cells into distinct populations with opposing hair bundle polarities
Saccular and utricular maculae lie PERPENDICULAR to each other meaning movement in any direction will stimulate a distinct subset of cells
i.e. head tilt to one side has opposite effects on corresponding hair cells of the other side (CaCO3 crystals involved as well)
Linear acceleration is dealt with by?
2 otolith organs - i.e. utricle and saccule
Angular acceleration is dealt with by?
3 semicircular canals (horizontal, anterior, posterior)
Describe the kinetic labyrinth
Semi-circular canals (SCC) involved
- In SCC, crista of ampulla (lots of hairs) detect head rotation in 3 orthogonal planes
- Cilia of hair cells embedded in gelatinous projection - “cupula”
- Hair cells stimulated by differential movement of endolymph and crest
- Kinocilia all oriented in same direction on each side of the head
Which artery supplies the inner ear
Anterior inferior cerebellar artery - also supplies cerebellum/other parts of the brain
Vestibular nerve primary afferents (superior and inferior) end in..?
Vestibular nuclei of brainstem and in cerebellum
What are the 4 vestibular nuclei, and how are they organised?
Superior, inferior, medial and lateral
Static labyrinth (otoliths) —> lateral and inferior
Kinetic labyrinth (SCC) goes to superior and medial
Where do vestibular nuclei project to?
- Spinal cord
- Nuclei of extra ocular muscles
- Cerebellum (ventral posterior and ventral lateral nuclei of thalamus)
- Centres of CVS + respiratory control
3 things which vestibulo-cerebellar pathway regulates
- Movement coordination
- Posture regulation
- VOR modulation
Vestibular system has resting discharge (nerve fibres giving info at a basal rate). What are the 3 states of the hair cells
- Resting
- Excitation
- Inhibition