Vestibular systems Flashcards
What are the functions of the vestibular system?
Gaze stabilisation.
Maintain spatial orientation- plane illusion or train illusion may impair this.
Self vs. world motion perception.
What vestibular structures are responsible for detecting angular acceleration?
3 semi-circular canals.
What vestibular structures are responsible for detecting linear acceleration?
2 otolith organs.
What connections does the vestibulo-ocular reflex have?
Ocular
Spinal
Autonomic
Cortical
What sensations are the different vestibular projections responsible for?
Vestibulo-ocular = nystagmus.
Vestibulo-spinal = unsteadiness.
Vestibulo-autonomic = nausea.
Vestibulo-cortical = vertigo.
What are the 2 components of the vestibular labyrinth?
Bony labyrinth- bounded by petrous temporal bone filled with perilymph.
Membranous labyrinth- filled with endolymph, contains receptor cells, located within the utricle, saccule and semi-circular canals.
Where are epithelial hair cells located in the vestibular system?
Macula- in utricle and saccule.
Crista- of ampulla (swelling of semi-circular canals).
Where do the primary afferent neurons of the vestibular system have their cell bodies?
Vestibular ganglion.
Where do the peripheral processes of the primary afferent neurons of the vestibular system terminate?
Macula and ampulla.
Where do the central processes of the primary afferent neurons of the vestibular system synapse?
Brainstem vestibular nuclei.
What are hair cells?
Mechanical transducers detecting static tilt and acceleration.
Embedded in a gelatinous matrix contain calcium carbonate crystals- uloconia.
Stereocilia are arranged in rows of varying heights, and there is a single long kinocilium.
What are the 2 types of nerve endings on hair cells?
Type I: chalice-like endings form ribbon synapses.
Type II: simple nerve terminals.
What is the transduction mechanism of vestibular hair cells?
Mechanoelectrical transduction mechanism similar to the cochlea.
Hair cell receptor potential: toward the kinocilium = depolarisation; away from the kinocilium = hyperpolarisation.
Ganglion cell discharge: toward the kinocilium = increased frequency; away from the kinocilium = decreased frequency.
What are the 4 main targets that the vestibular nuclei project to?
Spinal cord.
Nuclei of the extraocular muscles.
Cerebellum.
Centres for cardiovascular and respiratory control.
How do the vestibular pathways influence the static labyrinth (otoliths)?
Vestibulospinal tract.
Antigravity muscles that contribute to upright posture and equilibrium.
Blood pressure.
How do the vestibular pathways influence the kinetic labyrinth (semi-circular canals)?
Medial longitudinal fasciculus (MLF).
Eye movements that ensure that the retinal image is kept stationary when the head moves.
Postural adjustments.
Cardiovascular and respiratory function.