week 7

Question 1

What are the vestibular functions?

Answer 1

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

Question 2

what is the fluid inside the endolymph and where is it created?

Answer 2

perilymph/endolymphatic sac

Question 3

Which part of the bony membranous labyrinth responds to linear motion/up and down

Answer 3

utricle

Question 4

which part of the bony/membranous labyrinth responds to horizontal movement?

Answer 4

saccule

Question 5

Semicircular canals stimulus/function

Answer 5

stim: rotational acceleration and deceleration
function: stabilization of vision

Question 6

semicircular canals reflex/structure

Answer 6

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

Question 7

otolith organs (utricle and saccule) stimulus/function

Answer 7

stimulus: head position relative to gravity. linear deceleration or acceleration
function: adjusts activity of LMN of postural muscles

Question 8

otolith organs reflex/structures

Answer 8

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

Question 9

Semicircular canals-what are they?

Answer 9

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

Question 10

efferent projection from vestibular nucleii

Answer 10

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

Question 10

Afferent peripheral vestibular pathway

Answer 10

receptors (hair cells)->afferent fibers->vestibular ganglia(scarpa’s ganglia)->synapse in vestibular nucleii
function: detect head motion and head position relative to gravity

Question 11

function of efferent projection from vestibular nucleii

Answer 11

sensory info about head movement and position, gaze stabilization, postural adjustments, ANS, consciousness

Question 12

function/origin/pathway of lateral vestibulospinal tract

Answer 12

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

Question 13

function/origin/pathway of medial vestibulospinal tract

Answer 13

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.

Question 14

what is the Vestibular ocular reflex

Answer 14

stabilize visual images during head movement
move eyes in direction opposite to head movement
suppresion of VOR from flocculonodular lobe of cerebellum

Question 15

what are some vestibular disorders?

Answer 15

vertigo-illusion of motion
nystagmus-peripheral
dysequilibrium-sense of imbalance
ataxia

Question 16

describe the neural circuitry of stimulation of the left horizontal semicircular canal resulting in VOR. Stimulation of the left semicircular canal results in:

Answer 16

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.