Exam 3 Week 14 ppt 11 & 12 Vestibular Central Connections Part 1 & 2 Flashcards
what type of neurons are the primary afferent fibers leaving the macular and ampular epithelium (macular organs and ampular organs)?
bipolar neurons
Where do the primary afferent fibers of the bipolar neurons leaving both the macular and ampular epithelium have their cell bodies?
•The maculae and cristae are innervated by bipolar neurons of the vestibular (Scarpa’s) ganglion
what nerve does the central process of the first order neurons from the macular and ampullar epithelium form?
The central processes of these bipolar neurons form the vestibular nerve
where does the vestibular nerve enter the brainstem?
(and what nerve was it part of)
enters the brain stem at the pontomedullary junction just medial to the acoustic portion of the vestibulocochlear nerve (CN VIII)
Where are the four vestibular nuclei found?
at the pontomedually junction
List the four vestibular nuclei:
- -Lateral vestibular nucleus
- -Inferior vestibular nucleus
- -Medial vestibular nucleus
- -Superior vestibular nucleus
Where do the vestibular nuclei get input from? (3)
- Vestibular nerve
- Cerebellum
- Other inputs
what does SSC stand for?
semi-circular canal
(not sure why it is SSC and not SCC)
what does the vestibular nerve bifurcate into?
-Bifurcates into short ascending and long descending branches to the vestibular nuclei.
Vestibular nerve: Which nuclei do inputs from the semicircula canals primarily go to?
What do they also sometimes go to?
-Semicircular canals inputs go primarily to
- medial vestibular nuclei
- superior vestibular nuclei
some go to
- lateral vestibular nuclei
- inferior vestibular nuclei
Vestibular Nerve: Which nuclei do inputs from maculae primarily go to?
-Macular inputs go primarily to the:
- lateral vestibular nuclei
- medial vestibular nuclei
- Inferior vestibular nuclei
what vestibular nuclei are related to eye movements?
what has major inputs into these nuclei?
- medial vestibular nuclei
- superior vestibular nuceli
-Semicircular canals inputs go primarily to medial and superior vestibular nuclei
what vestibular nuclei are closely related postural adjustments?
what has major inputs into these nuclei?
- lateral vestibular nuclei
- medial vestibular nuclei
- inferior vestibular nuclei
-Macular inputs go primarily to the lateral, medial and inferior vestibular nuclei
does the vestibular nuclei receive input from the cerebellum?
Yes!
Just as there are projections from the vestibular nerve and nuclei into the cerebellum there are Cerebellar projections to vestibular nuclei
Where do the cerebellar projections to the vestibular nuclei travel?
where do they come from?
and are they inhibitory or excitatory?
Travel through the inferior cerebellar peduncle to all nuclei
Cerebellar cortex of flocculonodular lobe: Inhibitory
Fastigial nucleus: Excitatory
These projections to and from the cerebellum go through the inferior cerebellar peduncle to all vestibular nuclei. There are Inhibitory projections from cerebellar cortex of flocculonodular lobe and Excitatory projections from the fastigial nucleus.
do any fibers from the semicircular canals travel to somehwere outside of the vestibular nuclei?
if so where?
-Some fibers from SSCs rise directly thru inferior cerebellar peduncle into the cerebellum
- End in the nodulus and perhaps the floccular cortex
- Collaterals end in the fastigial nucleus
Some fibers from semicircular canals rise directly thru inferior cerebellar peduncle into the cerebellum to End in the nodulus and perhaps the floccular cortex with Collaterals ending in the fastigial nucleus
are there any additional connections involving vestibular nuclei besides the primary afferent and cerebellar inputs?
If so, what are they?
Yes
There are Commissural Connections
what are the commussural connections between?
there are considerable Commissural Connections Between most of the nuclei but
most prominent between the contralateral
- medial vestibular nuclei and
- superior vestibular nuclei.
are the commissural connections primarily inhibitory or excitatory?
why?
. These commissural connections are Primarily inhibitory so increased activity on one side inhibits activity on the other. Remember of course that vestibular input is bilateral – cannot accelerate one side of head & not other.
describe what happens in relationship to the vestibular commissural connections when the head rotates right.
- Right vestibular nuclei more 1° afferent excitation
- Left vestibular nuclei less 1° afferent excitation
- Commissural connections will match this pattern of input to the vestibular nuclei so works together with 1° afferent input
So with say rotation to the right, the right vestibular nuclei will have additional excitation by the primary afferents and the left vestibular nuclei will receive less excitation. The excited right vestibular nuclei will produce inhibition of the left vestibular nuclei and there will be less inhibition of the right vestibular nuclei by the left vestibular nuclei. So you can see that the vestibular primary afferents and commissural connections work together
why are commissural Connections of the vestibular nuclei imortant? (2)
- -Important for comparison of activities of the pairs of semicircular canals and macular structures
- -Mechanism by which compensation can occur for unilateral vestibular damage
Commissural Connections are Important for comparison of activities of the pairs of semicircular canals and macular structure. With the similarity of function of commissural connections to that of the primary afferent input, these commissural connections are a Mechanism by which compensation can occur for unilateral vestibular damage
what are some other inputs to the vestibular nuclei besides commissural, primary afferents, and cerebellar inputs?
-Some inputs from spinal cord & brainstem complete the picture
There are also Other Inputs to Nuclei as there are Some inputs from spinal cord & brainstem complete the picture
Where do central projections from the vestibular nuclei go?
•Projections from Vestibular Nuclei to Thalamus & Cerebrum
- -Projections from superior, medial & lateral vestibular nuclei to ventroposterolateral (VPL) nucleus of thalamus
Now for the conscious awareness of head position and acceleration there are vestibular nuclearProjections from Vestibular Nuclei to Thalamus & Cerebrum. However this is the Least robust of any sensory system
There are Projections from superior, medial & lateral vestibular nuclei to ventroposterolateral (VPL) nucleus of thalamus
how does the vestibular system compare to other sensory systems in its strength of central connections?
the vestibular system is the Least robust of any sensory system
Are projections from the vestibular nuclei ipsilateral, contralateral, or bilateral?
what does this result in?
-Projections bilateral to thalamus so activity bilaterally represented in cerebral cortex
Projections from the vestibular nuclei to the thalamus are bilateral so activity is also bilaterally represented in cerebral cortex.
How many cortical areas receive projections from the VPL nucleus of the thalamus from the vestibular system?
4
What are the four cortical areas that receive projections from the VPL nucleus of the thalamus from the vestibular system?
The projections from the ventroposterolateral (VPL) nucleus of thalamus are to 4 cortical areas related to vestibular function in insula and parietal lobe
what are the functions of the cerebral vestibular areas?
- -Sense of body & head position but not be a perceptual necessity
- -We usually rely more on Vision for the sense of movement
- -We usually rely more on Proprioception for sense of position
- -This Same priority pattern is seen in balance & reflexes
Cerebral Vestibular areas plays a role in sense of body & head position but not normally cued into it as perceptual necessity. We are more perceptually cued into vision and proprioception. We rely on vision more for the sense of movement, then proprioception and then vestibular sensation. We rely on proprioception more for the sense of position along with vision. We see the same priorities for balance reflexive responses as well
are there connections between the reticular formation and the vestibular nucei?
Yes
There are strong connections between the vestibular nuclei and the Reticular Formation.
Describe the connections between the Reticular formation and the vestibular nuclei?
include function
- -Vestibular nuclei Connections with UMN of reticulospinal tracts –
- complementary to vestibulospinal tract control of balance & posture
- -Vestibular Connections through RF to hypothalamus
- for control of autonomic responses to vestibular input
- -Nausea, vomiting, pallor and perspiration associated with overstimulation of vestibular system or vestibular system damage
- for control of autonomic responses to vestibular input
There are strong connections between the vestibular nuclei and the Reticular Formation. There are Connections with UMN of reticulospinal tracts which are complementary to vestibulospinal tract control of balance & posture. There are also Connections through RF to hypothalamus for control of autonomic responses to vestibular input. Nausea, vomiting, pallor and perspiration associated with overstimulation of vestibular system or vestibular system damage
Describe the function of the vestibular connection with UMN of reticulospinal tracts:
- Vestibular nuclei Connections with UMN of reticulospinal tracts:
- complementary to vestibulospinal tract control of balance & posture
- Vestibular Connections through RF to hypothalamus
for control of autonomic responses to vestibular input
-Nausea, vomiting, pallor and perspiration associated with overstimulation of vestibular system or vestibular system damage
Describe the function of the vestibular connections through the RF to the hypothalamus
-Vestibular Connections through RF to hypothalamus
- for control of autonomic responses to vestibular input
- -Nausea, vomiting, pallor and perspiration associated with overstimulation of vestibular system or vestibular system damage
There are also Connections through RF to hypothalamus for control of autonomic responses to vestibular input. Nausea, vomiting, pallor and perspiration associated with overstimulation of vestibular system or vestibular system damage
Describe the vestibular connections to the cerebellum
- -Direct projection of 1° afferents into cerebellum thru inferior cerebellar peduncle
- -Projections from vestibular nuclei
- Come form most nuclei
- Through the inferior cerebellar peduncle
- Vestibulocerebellar projections go primarily to flocculonodular lobe & uvula with collaterals going to the fastigial & dentate nuclei and other areas of cortex
- For balance, reflexes and movement coordination
We have mentioned before the connection of the vestibular nuclei with the flocculonodular lobe of the Cerebellum. As we have mentioned previously there are Direct projection of 1° afferents and Projections from most vestibular nuclei into cerebellum thru inferior cerebellar peduncle. Vestibulocerebellar projections go primarily to flocculonodular lobe with collaterals going to the fastigial & dentate nuclei and some other areas of cortex. These connections are for balance, reflexes and movement coordination
what do the lateral and medial vestibular nuclei give rise to?
Two UMN descending tracts
- lateral vestibulospinal tract (LVST)
- medial vestibulospinal tract (MVST)
Then there is the vestibulomotor system with the lateral and medial vestibular nuclei having upper motor neurons which give rise to the the descending lateral and medial vestibulospinal tracts
What is the vestibulomotor system?
Then there is the vestibulomotor system with the lateral and medial vestibular nuclei having upper motor neurons which give rise to the the descending lateral and medial vestibulospinal tracts
Describe the anatomy of the Lateral Vestibulospinal tract (4)
•Lateral vestibulospinal tract (LVST)
- –Arises from lateral vestibular nucleus
- –Larger of the two tracts
- –Excitatory to ipsilateral spinal cord extensor nuclei
- –Biggest input is from the cerebellum
Lateral vestibulospinal tract (LVST) Arises from lateral vestibular nucleus, is the Larger of the two tracts with Excitatory primarily ipsilateral effects on spinal cord extensor nuclei throughout the spinal cord. The biggest input is from the cerebellum but remember there are also considerable inputs form the macular epithelium and some input from the semicircular canals into the lateral vestibular nucleus
What is the function of the Lateral Vestibulospinal Tract?
•Lateral vestibulospinal tract (LVST)
–Facilitates and maintains extensor tone in limbs and trunk – antigravity response
LVST
Lateral Vestibulospinal Tract
Describe the anatomy and function of the Medial Vestibulospinal tract (4)
•Medial vestibulospinal tract (MVST)
- –Descends from medial vestibular nucleus
- –Functionally descends only to the cervical spinal cord
- –Functions to stabilize the head in space when the body is moving when walking around
- –Functions to stabilize the eyes (& head) and maintain gaze during body movements
Medial vestibulospinal tract (MVST) Descends from medial vestibular nucleus primarily to the cervical spinal cord and Functions to stabilize the head in space when the body is moving when walking around. Also the Medial vestibulospinal tract (MVST) Functions to stabilize the eyes (& head) and maintain gaze during body movements.
MVST
Medial Vestibulospinal tract
Describe the Vestbiular nuclei projections to extraocular motor neurons:
name
pathway
function
- They are called the Medial Longitudinal Fasciculus
- •projections from the superior and medial vestibular nuclei project to nuclei of CN III, IV, VI
- •Coordinate eye movement with body movement or head movement (vestibulo-ocular reflex)
Vestibular nuclei also Projections to Extraocular Motor Neurons. Medial Longitudinal Fasciculus (MLF) projections from the superior and medial vestibular nuclei project to nuclei of CN III, IV, VI. . The MLF has a laterality pattern but effect projects bilaterally
These vestibular projections to the extraocular lower motor neuron nuclei are important for Coordinate eye movement with body movement or head movement (vestibulo-ocular reflex). We will talk more about this function in a later video.
MLF
Medial Longitudinal Fasciculus
