Neuroanat 9

Front 1

Semicircular Canals responds to

Back 1

ANGULAR velocity, 3 ducts (anterior,posterior,lateral or horizontal) each with an ampulla that has the hair cells embedded in the cristae (same depol/hyperpol pattern as auditory system)

Front 2

Utricle and Saccule respond to

Back 2

LINEAR acceleration, utricle is in the vertical plane and saccule is in the horizontal plane, hair cells embedded in maculae

Front 3

otoliths organs are stones that sit on the macule and they lag during

Back 3

acceleration before they pick up enough inertia to move . As we tilt, otoliths tilled as well and creates a shearing force that measures the change in acceleration– this allows the utricle and saccule to detect linear acceleration

Front 4

Hair Cells of the vestibular system– collect sensory info and

Back 4

send it to brain via vestibular division of CN8

Front 5

Hair cells type 1 characteristics

Back 5

firing rate proportional to velocity of head – post synaptic efferents, K+ currents, large terminal endings. Contacted by calyx

Front 6

Hair cells type 2 characteristics

Back 6

firing rate proportional to acceleration of head (BACKGROUND firing) – contacted by boutons, presynaptic efferents, similar to auditory hair cells

Front 7

- As opposed to auditory system, hair cells in vestibular system have kinocillium which is important to define

Back 7

the axis of movement. Movement of hair bundle (sterocilia) towards kinocilium causes excitation, and movement in any other direction causes inhibition. Movement toward kinocillium opens mechanotransduction channels located at tips of sterocilia and K flows in depolarizing the hair cell and causing synaptic transmission

Front 8

Adaptation of stereocilia

Back 8

(resetting of sterocilia) is done by a motor “Myosin” this means, if we tilt our head, after a while we get used to it and forget that it is tilted

Front 9

An ongoing background activity firing by hair cells is neccesary to

Back 9

detect changes

Front 10

Irregular fibers are

Back 10

very sensitive increase or decrease to detect a change (if we tilt head, one side of head increases, other decreases), found in central zone. They are phasic

Front 11

Regular fibers exhibit

Back 11

background activity, found in periphery and it is tonic

Front 12

- Boutons afferents

Back 12

only contact type 2 and they are insensitive and regular

Front 13

- Calyx only afferents

Back 13

contact only type 1 and are very sensitive and irregular

Front 14

- Dimorphic afferents

Back 14

contact type 1 and 2 HC. If in the periphery they are regular, if in the center (where small otoliths are) they are irregular

Front 15

Primary afferents pathway

Back 15

primary afferents -> vestibular ganglion -> 4 primary vestibular nuclei -> Middle Longitudinal Fasciculus (MLF) ->secondary nuclear targets ->eye/neck muscle targets (to coordinate body and head and eyes)

Front 16

Superior Vestibular nucleus receives input from

Back 16

cristae

Front 17

Lateral Vestibular nucleus receives input from

Back 17

macula

Front 18

Medial Vestibular nucleus receives input from

Back 18

cristae and macula

Front 19

Inferior Vestibular nucleus receives input from

Back 19

saccular macula only

Front 20

- Secondary nuclear targets

Back 20

: interstitial nucleus of Cajal, rostral interstitial nucleus of MLF, Paramedian pontine reticular formation-PPRF (horizontal eye movements), nucleus raphe interpositius, nucleus perpostus hypoglossi (position and velocity info, involved in fixation and horizontal/vertical eye movements)

Front 21

Medial longitudinal fasciculus ascending and descending is for

Back 21

eye movement coordination

Front 22

runs with MLF (all the way up and down from CN nuclei of 3,4,6 to cervical SC), coordinates eye movements with head movements (gaze pathways

Back 22

Medial vestibulospinal tract

Front 23

extends all the way down to the sacral level of SC, related to posture and gait (ie: keeping gaze steady/level while walking)

Back 23

Lateral vestibulospinal tract

Front 24

– extends to cerebellum to vermis/fastigial nucleus via juxtarestiform body, concerned with saccades –learned movements

Back 24

Vestibulocerebellar tract

Front 25

extends to thalamus (VPI = ventral posterior inferior nucleus) and cortex, path for conscious perception of head movement
- Usually unpleasant sensations – nausea, vertigo, dizziness (vestibulothalamic pathway  cortex)

Back 25

Vestibulothalamocortical tract

Front 26

reflex that moves your eyes to maintain fixation on an object when you move your head in opposite direction

Back 26

Vestibular Ocular Reflex

Front 27

– being able to turn to another moving target (ie: train and telephone poles, switch to next one etc)

Back 27

Optikinetic Nystagmus Reflex

Front 28

- Gaze stabilization

Back 28

fixation (nucleus preposititius hypoglossi and interstitial nucleus of Cajal), VOR (vestibular nuclei and MLF), OKN (retina, pretectum

Front 29

- Gaze shifting

Back 29

smooth pursuit, saccades, vergence

Front 30

Irregular afferents control

Back 30

controls posture, larger and thicker fibers that mainly go to large muscles in legs
- Control gait and balance – via lateral vestibulospinal tract

Front 31

Sensorimotor coordination

Back 31

Cerebellum
Learned movements

Front 32

Conscious Perception of vestibular sensations

Back 32

Nausea, vertigo, dizziness

Front 33

Vestibular autonomic (orthostatic) responses

Back 33

Adjust blood pressure and respiration during movement and postural alterations

Front 34

- Motion sickness

Back 34

discordance between visual and vestibular systems  dizziness, lightheadness, nausea, vomiting

Front 35

- Nystagmu

Back 35

rapid and slow eye movements back and forth

Front 36

- Menier’s disease

Back 36

nystagmus, vertigo, tinnitus, unilateral deafness, nausea and vomiting

Front 37

- Rotational test

Back 37

spin around in chair, tests for physiological nystagmus