32-33. Vestibular Proprioception

proprioception

incoming information about positions of head and body in motion and at rest

vestibular input for ______ proprioception and somatosensory input for ________ proprioception

head, body

__________ integrates the two sources of proprioceptive input to produce accurate movement

cerebellum

3 main functions of output from vestibular nuclei

1. maintain visual fiield

2. control level head position

3. compensate for head movements to maintain upright stance

what structures make up the peripheral vestibular system?

vestibular apparatus and vestibular nerve and ganglia

what structures make up the central vestibular system?

vestibular nuclei in medulla and their projections to cerebellum??

A strictly ___________ vestibular problem will not produce somatosensory proprioceptive deficits or UMN signs in the limbs

peripheral

What helps maintain a steady visual field?

vestibular nucleus projections to CNN 3, 4, 6

vestibulo-ocular reflex

Coordination of motion information with visual information that allows you to maintain your gaze on an object while you move.

-direction in which the head turns determines which side of the system drives the reflex

T/F: vestibulo-ocular reflex is a normal form of nystagmus

true, keeps visual field steady until brain circuit resets gaze in direction of new visual field

why do these CN innervate?

a. CN III

b. CN IV

c. CN VI

a. DR, MR, VR, VO

b. DO

c. LR

T/F: vestibular receptors are always active

true- even when head is still/ balanced tonic activity is equal

what should occur when head turns to the left?

Explain short and fast phase of the vestibular pathway

As head turns left eyes slowly turn to right (slow phase) and if head continues to turn left, eyes quickly jerk back to left and reset to center (fast phase)

The fast phase of nystagmus is always toward which side?

more active vestibular system

Explain how spontaneous nystagmus can develop from a unilateral lesion?

side that is damaged no longer sends tonic activity. Brain percieves asymmetry in activity as movement of head to to more normal 'active' side although head is not moving

that fast phase is (towards/away) from the side of the lesion when the lesion is in peripheral vestibular structures or vestibular nuclei

away

what is most common type of nystagmus?

horizontal

vestibulo-colic reflex

incoming vestibular info is used by vestibular nuclei to direct neck muscle contraction

explain pathway of vestibulo-colic reflex

vestibular nerve -> ipsilateral vestibular nuclei -> descending medial longitudinal fasiculus -> ipsilateral cervical spinal grey matter

Will the head tilt towards or away from the lesioned (less active) side when peripheral or central components of the vestibular system are unilaterally lesioned?

towards

what reflex induces changes in head position based on changes in posture?

vestibulospinal reflex

explain pathway of vestibulospinal reflex

vestibular nerve -> ipsilateral vestibular nuclei -> ipsilateral spinal cord ventral funiculus -> vestibulospinal tract -> ipsilateral spinal gray matter LMNs

T/F: upright stance is maintain when the head is moved horizontally by increasing activity on opposite side and decreasing activity on moving side

false, other way around

any UMN signs will signal that it is a central nervous system lesion showing postural deficits. Will the lesion be contralateral or ipsilateral to the side where there are deficits?

ipsilateral

in either peripheral or central vestibular lesion why does the animal lean, circle or roll toward the lesioned side?

the normal side has enhanced extensor thrust compared to lesioned side with slow/ diminished extensor thrust