week 7 Flashcards
What are the vestibular functions?
conscious awareness of head movement and head position relative to gravity
gaze stabilization by controlling eye movement when the head moves
postural adjustment
autonomic function and consciousness
brainstem/reticular formation involved
what is the fluid inside the endolymph and where is it created?
perilymph/endolymphatic sac
Which part of the bony membranous labyrinth responds to linear motion/up and down
utricle
which part of the bony/membranous labyrinth responds to horizontal movement?
saccule
Semicircular canals stimulus/function
stim: rotational acceleration and deceleration
function: stabilization of vision
semicircular canals reflex/structure
VOR vestibulo-ocular reflex stabilizes gaze during head movements by triggering eye movements that are opposite and equal in speed to head movements
structure: MLF
otolith organs (utricle and saccule) stimulus/function
stimulus: head position relative to gravity. linear deceleration or acceleration
function: adjusts activity of LMN of postural muscles
otolith organs reflex/structures
reflex: VCR vestibulocollic reflex-compensatory response that helps stabilize the head in space when the body moves by generating a command to move the head in the opposite direction of the current motion
structures: medial/lateral vestibulospinal tracts
Semicircular canals-what are they?
3 rings, arranged perpendicular to each other, open into utricle, head is flexed 30 degrees, horizontal canals are parallel to floor, ant. and post. canals are vertical.
Information from here used to stabilize vision
efferent projection from vestibular nucleii
vestibulospinal tract (control limb and axial muscles)->brainstem nucleii(CN3,4,6)->small ascending thalamocortical projection(conscious awareness of oritentation and motion of head and balance)->vestobulocerebellum->vestibucollic CN11->vestibuloautonomic to reticular formation
Afferent peripheral vestibular pathway
receptors (hair cells)->afferent fibers->vestibular ganglia(scarpa’s ganglia)->synapse in vestibular nucleii
function: detect head motion and head position relative to gravity
function of efferent projection from vestibular nucleii
sensory info about head movement and position, gaze stabilization, postural adjustments, ANS, consciousness
function/origin/pathway of lateral vestibulospinal tract
originates in the lateral vestibular nucleus, descends to ventral regions of entire spinal cord white matter, terminates in ventral gray horn. Function: postural control and balance
function/origin/pathway of medial vestibulospinal tract
originates in medial vestibular nucleus. innervates muscles involved in supporting the head, only passes in cervical region. function is to position head and neck in response to vestibular input.
what is the Vestibular ocular reflex
stabilize visual images during head movement
move eyes in direction opposite to head movement
suppresion of VOR from flocculonodular lobe of cerebellum
what are some vestibular disorders?
vertigo-illusion of motion
nystagmus-peripheral
dysequilibrium-sense of imbalance
ataxia
describe the neural circuitry of stimulation of the left horizontal semicircular canal resulting in VOR. Stimulation of the left semicircular canal results in:
Movement of the endolymph to bend and facilitate the vestibular portion of CN VIII. These nerve fibers will synapse in the left vestibular nuclei and project fibers bilaterally through the medial longitudinal fasciculus. Contralateral fibers facilitate the right rectus muscle and left medial muscle and ipsilateral fibers facilitate the left rectus muscle and right medial muscle.
