vestibular system 1 and 2 Flashcards
Hair cell neurotransmitter
Glutamate and aspartate
These are excitatory
Kinocilium
Long cilia of hair cells, function as strain gauges that transducer mechanical stimuli.
Depolarization and hyperpol of hair cells
Cells depolarize when steriocilia bend toward the kinocilia, and hyperpol when they bend away.
Static labyrinth
Comprised of the saccule and the utricle
Provides information via vestibular afferents about head position and linear acceleration.
Macula of static labyrinth
Mac of the utricle are horizontally oriented and so the steriocilia project vertically from it.
Mac of saccule are vertically oriented and thus steriocilia project horizontally from it.
Detect static position of the head relative to gravity and linear acceleration.
Otolithic membrane
Membrane steriocilia and kinocilia are embedded in
Mass of oto creates pull on the steriocilia in the direction of gravity
Macula utricle
Kinocilia are oriented toward the srtiola
Macula sacculi
Kinocilia are oriented away from the striola.
Kinetic labyrinth
Mede by the semicircular canals
Crista
Saddle shaped ridges that contain hair cells
Found in the ampulla
Movement of endolymph relative to cristae allows detection of angular acceleration and deceleration in three planes
Capula
Gelatinous structure that encapsulates the cristae and is attached to epithelial lining
Cupola move in the opposite direction of head movement and facilitate deflection of cilia.
Kinocilia position for anterior and posterior and horizontal canals
In the horizontal canals the kino are oriented toward the utricle while kin of ant and post canals are oriented away from the utricle
This endolymph toward utricle will depolarize the horizontal canal.
Movement away from the utricle will depolarize ant and post canals
Ant and post canals
Sensitive to roll and pitch movements the differential input codes for angular movement
Vestibular nuclear complex
Located dorsally in the pons and medulla between lateral part of 4th vent and inferior cerebellar peduncle.
Division of vestibular nerve as it enters the brain stem
It splits into ascending fibers and descending fibers
Ascending go to the superior vestibular nucleus, and descending go to the medial and inferior nuclei
Vestibular fiber trends
Kinetic labyrinth fibers primarily go to the superior and medial nuclei while static lab fibers will go to the medial and inferior nuclei
Commissural connections
Between vest nuclei on either side for comparison of information coming from both sides
These connections also allow for vestibular compensation where postural reflexes are recovered after trauma or disease.
Vestibular input
From the cerebellum- floculonodular lobe to sup, med and inf nuc, lateral vermis to the lateral nuc, fstigial nuc to the lat and inferior vest nuclei
Spinal cord: proprioceptive info from spinovestibular tract.
Oculomotor system: accessory optic system.
Vest output
To the cerebellum , spinal cord and oculomotor system
Minor output to the insular cortex via thalamus.
Medial vestibulospinal tract
Travels via the MLF to the cirvical spine and innervates the medial group of motor neurons in the anterior horn of the spinal cord.
Involved in integration of head and eye movements associated with changes in body position.
Arises from medial and inferior vest nuc and has crossed and uncrossed fibers.
Lateral vestibulospinal tract
Involved in adjusting trunk position and orientation in respons to input from the static and kinetic labyrinths.
Travels the length of the sp crd, innervates medial and lateral groups of the ventral horn
Facilitates muscles that maintIn upright posture and balance
Vestibuloocular system
Stimulation of semicircular canals causes conjugate eye movements in the same plane as the canal
Stim of horizontal canal causes eye movement in a horizontal plane
Enables movement of eyes such that focus on an object can be maintained even when the head is in motion.
Vestibulo-ocular reflex
Ipsilateral projections are inhibitory and contra lateral projections are excitatory
3 neuron reflex arc- primary afferent, vestibular nuclear neuron, oculomotor motorneurons.
Projections from med and sup vest nuc project to oc mot nuclei via MLF
This functions to coordinate functionally and link pairs of eye muscles.
Damage to the vestibular system
Vertigo, ataxia, nystagmus, nausea and vomiting
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