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Neuroscience Block 3 > Cerebellum > Flashcards

Cerebellum Flashcards

0
Q

What is the major role of the cerebellum?

What three specific features do we check for?

A 
To monitor and quality check to make sure planned action and executed action are coordinated and timed well 
Specifically: 
1.Balance/equilibrium
2. Fine motor skills  (motor memory) 
3. eye movement
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1
Q

What is the difference between an ataxia and a tremor?
Insult to what brain area would cause ataxia?
Insult to what brain area would cause tremor?

A

Ataxia is shaking when attempting a task.
Tremor is moving or shaking when you are not doing anything.
Ataxia is associated with the cerebellum
Tremor is frequently associated with the basal ganglia

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2
Q

Dysfunction with the cerebellum would affect what?

A

Smoothness of motion, balance, fine motor control, eye movement and would cause ataxia

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3
Q

What area of the brain send input to the cerebellum?

Where does the cerebellum signal to?

A
  1. Cortex via pontine relays
  2. vestibular system- to orient the head
  3. Spinocerebellar tract

Efferents go to thalamus (VA/VL) and brainstem structures and through these structures, influence motor neurons.

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4
Q

What nuclei of the thalamus receive input from the cerebellum?
What cells in the thalamus then coordinate with UMNs?

A

VA/VL

Betz cells

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5
Q

What tracts influence the lower motor neurons?

A

Corticospinal tract (indirectly influence by cerebellum)

Brainstem pathways like:

  1. Rubrospinal from the red nucleus in the midbrain
  2. Vestibulospinal tract from vestibular complex
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6
Q

What are the two type of excitatory axons that carry information to the cerebellum?
Which is MOST of the information reaching the cerebellum conveyed by?

A
  1. Mossy fibers-indirect via activation of the granule cell
  2. Climbing fibers-direct from the inferior olive

Most afferent information comes from the mossy fibers

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7
Q

Where do mossy fibers terminate in the cerebellum?

What else is found here?

A

In the internal granular layer in areas called cerebellar glomeruli.
The cerebellar glomeruli is comprised of:
1.Mossy fiber axons
2. Granule cell dendrites
3. purkinje cell axons

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8
Q

Once the mossy fiber excites the granule cell, what happens?

A

The granule cell axon ascends and excites purkinje cells with their parallel fibers

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9
Q

A purkinje cell receive input from how many granule cells?

A

One million

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10
Q

Where does the climbing fiber originate?

What cells do they excite? About how many? Is the excitation direct or indirect?

A

Inferior olivary nucleus on the contralateral side

The climbing fiber directly excites roughly 10 purkinje cells

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11
Q

Purkinje cells receive information from how many climbing fibers?

A

One

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12
Q

Aside from the purkinje cell, where do mossy fibers and climbing fibers send collateral branches?

A

Deep cerebellar nuclei

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13
Q

Inhibitory signals on the purkinje cell come from 3 sources. What are they? Is the inhibition direct or indirect?

A

Direct inhibition comes from the stellate cells on the purkinje dendrite and basket cells on the purkinje cell bodies.

Indirect inhibition comes from the Golgi cells which inhibit granule cells ( thus turning off the activating parallel fibers)

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14
Q

What cell is the only source of output from the cerebellar cortex?
Where do they send their efferents?
Are the signals inhibitory or excitatory?

A

The purkinje cell
Most projections go to the deep cerebellar nuclei
Purkinje cells from the flocculonodular lobe send projections directly to vestibular nuclei
Signal is inhibitory

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15
Q

What are the two types of projections that leave the cerebellum?

A
  1. Purkinje cells from flocculonodular lobe

2. Axons from the deep cerebellar nuclei

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16
Q

What are the three “functional” divisions of the cerebellum?

A
  1. Vestibulocerebellum (head)
  2. Spinocerebellum (body)
  3. Cerebrocerebellum (fine control)
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17
Q

What is the other name for the vestibulocerebellum?
What three functions is it concerned with?
What are the cerebellar components?

A
  1. Flocculonodular lobe
  2. Balance, equilibrium, eye movements
  3. Flocculus and nodulus
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18
Q

What is the input to the vestibulocerebellum?

What is the output from the flocculonodular lobe?

A

Projections from the inner ear and vestibular nuclei of the brainstem
Output goes directly back to the vestibular nuclei in the brainstem

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19
Q

Specifically, what parts of the ear send signal to the flocculonodular lobe of the cerebellum?

A

The vestibular labyrinth (semicircular canals and otoliths organs)

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20
Q

Where are the vestibular nuclei located? Where do they send projections?

A

The pons and medulla and send projections to the vestibulocerebellum from the inferior nucleus of the vestibular system

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21
Q

Are projections from the vestibular labyrinth ipsilateral or contralateral to the cerebellum?
Why do they provide the brain with information about?

Are projections from the vestibular nuclei to the cerebellum ipsilateral or contralateral?

Through what structure do vestibular inputs enter the cerebellum?

A

They supply the ipsilateral information about the position and movement of the head

Vestibular nuclei supply bilateral information
Vestibular labyrinth and vestibular nuclei input enter the cerebellum by way of the inferior cerebellar peduncles

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22
Q

What is the primary vestibular afferent?

What is the secondary vestibular afferent?

A

Primary is from the vestibular labyrinths (semicircular canals and otoliths)
Secondary is from the vestibular nuclei

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23
Q

What is the primary afferent tract into the cerebellum?

What is the primary efferent tract out of the cerebellum?

A

The primary afferent tract is the inferior cerebellar peduncles
Superior cerebellar peduncle is the major efferent (except for the unconscious sensation from L2 and below which is an afferent through the superior)

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24
Q

What is the oldest division of the cerebellum?

A

The vestibulocerebellum

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25
Q

Where do purkinje cells from the vestibulocerebellum send direct inhibition?

A

To the vestibular nuclei in the brainstem (medial and superior nuclei mostly with a little to the lateral nuclei)

26
Q

What specific nuclei in the vestibular nuclei send afferents to the cerebellum?
Which nuclei receive efferents back from the cerebellum?

A

The inferior nuclei sends the afferents

The medial and superior (and a tiny bit of the lateral) receive signal back

27
Q

What do projections to the medial and superior vestibular nuclei coordinate?
How is this achieved?

A

Movements of the eyes relative to movements of the head.

This is achieved by the medial and superior vestibular nuclei sending efferents to cervical motor neurons, cranial nerve nuclei and the MLF

28
Q

What do cerebellar projections to the lateral vestibular nuclei influence?

A

The lateral vestibular nuclei influences the activity of axial muscles and limb extensors via the lateral vestibulospinal tracts to maintain posture and balance

29
Q

What are the cerebellar components of the spinocerebellum?

A 
Vermal region:
Cerebellar vermis (except the nodulus) 
Fastigial nuclei 
Paravermal region: 
Interposed nuclei (emboliform and globose)
30
Q

From where does the spinocerebellum receive input?

A
  1. The spinal cord via spinocerebellar tracts.
  2. Cuneocerebellar tracts
  3. Trigeminocerebellar tracts
  4. Vermal portion receive input from the vestibular nuclei
  5. Visual input and inferior Olivary nucleus
31
Q

What is the path for the dorsal spinocerebellar tract, cuneocerebellar tract and trigeminocerebellar tract into the cerebellum?

What is the path for the ventral spinocerebellar tract?

A

They all remain ipsilateral and go through the inferior cerebellar peduncle

The ventral spinocerebellar tract originates in the contralateral lumbosacral gray (L2 and down), crosses the midline to ascend in the Tract, enters the superior cerebellar peduncle and recrosses into the cerebellum ipsilateral to it’s origin

32
Q

Sensory information from What muscle groups enters the Vermal portion of the spinocerebellum?
Sensory info From what muscle groups enters the paravermal portion of the spinocerebellum?

A

Vermal- proximal muscle groups

Paravermal- distal muscle groups

33
Q

Projections from the Vermal portion of the spinocerebellum travel to what deep nuclei?
From this nuclei, where do the projections go?

A

Vermal portion of spinocerebellar projects to the fastigial nucleus which projects through the inferior cerebellar peduncle to:

  1. the lateral vestibular nuclei bilaterally (head and neck)
  2. The reticular nuclei in the brainstem (antigravity muscles)
34
Q

Projections from the paravermal part of the spinocerebellum go to what deep nucleus?
From this nucleus, where does signal travel?

A

Paravermal signal goes to the interposed nuclei which send their fibers through the superior cerebellar peduncle to:

  1. Contralateral magnocellular red nucleus
  2. VA/VL nuclei in the contralateral thalamus
35
Q

Where do magnocellular nuclei in the red nucleus receive input from?
Where do they send output?

A
  1. Receive input from the contralateral interposed nuclei of the cerebellum
  2. Send info that crosses and descends in the Rubrospinal tract to control lateral forelimbs (projection ends in the cervical spinal cord)
36
Q

Where do the VA/VL nuclei of the thalamus receive input from?
Where do they send input?

A
  1. Receive info from the interposed nuclei

2. Project to the motor and promoter areAs of the cerebral cortex to control distal muscle groups

37
Q

What is the youngest region of he cerebellar cortex?

A

The Cerebrocerebellum

38
Q

What is the function of the Cerebrocerebellum?

A

Fine motor control
Planning, initiation, timing of complex movements
Motor memory

39
Q

Where does the majority of the input to the Cerebrocerebellum come from?
What brainstem structure do they travel through?

A

The contralateral cerebral hemisphere (specifically motor, somatosensory and visual cortex areas)
The signal descends cerebral peduncles to synapse with neurons in the basal pons. The basal pons sends axons to the contralateral middle cerebellar peduncle.

40
Q

What brainstem structure sends afferents to every division of the cerebellum?
Signal enters the cerebellum via what structure?

A

The inferior Olivary nucleus sends projections via the contralateral inferior cerebellar peduncle

41
Q

The purkinje fivers of the Cerebrocerebellum send signal to what deep nucleus?
Where does this nucleus send it’s signal?

A

Signal goes to the ipsilateral dentate nucleus which excites the:

  1. contralateral red nucleus parvocellular nuclei
  2. VA/VL of the thalamus
42
Q

Where do parvocellular neurons from the red nucleus receive and send projections?

A

Receive signal from the dentate nucleus of the cerebellum

And send signal to the ipsilateral inferior olive to make a feedback look with the cerebellum

43
Q

What afferents go through the inferior cerebellar peduncle?

A
  1. Dorsal spinocerebellar, cuneocerebellar, trigeminocerebellar (ipsilateral)
  2. Contralateral inferior Olivary nucleus
  3. Vestibular nuclei and labyrinth
44
Q

What efferents exit the inferior cerebellar peduncle?

A
  1. Flocculonodular lobe and vermal portion to vestibular nuclei
  2. Reticular nuclei of the brainstem
45
Q

What are the afferents of t he middle cerebellar peduncle?

What are the efferents?

A

Afferents- cerebral input to the Cerebrocerebellum via the contralateral basal pons
Efferents-none

46
Q

What are the afferents that travel through the superior cerebellar peduncle?
What are the efferents that leave it?

A

Afferents- ventral spinocerebellar tract
Efferents-
1. Excitatory fibers leaving the dentate to the contralateral parvocellular red Nucleus and va/VL
2. Excitatory fibers leaving the interposed to contralateral magnocellular red nucleus and va/VL
3. Fastigial fibers

47
Q

What three things are required for motor learning?

A
  1. What is the task (planned movement)
  2. Did I achieve the task? (executed movement)
  3. You need the motor ability to make an adjustment
48
Q

How does the vestibule-ocular reflex (VOR) help you to do?

A

Keep your eyes on a target by counter-rolling the eyes in the opposite direction when the head is moved

49
Q

What is the primary stimuli for the VOR and why?

A

The vestibular afferent is the primary stimuli for the VOR because it has a shorter latency then visual feedback

50
Q

If goggles are placed on a subject to reduce the optical image size, what happens to the eye movement triggered by the VOR?

A

The eye movement will initially be too large because it is correlating with the amplitude of the head movement when the response should be smaller because of the smaller visual field.

51
Q

What is the stimulus for motor learning?

What is it attempting to reduce?

A

Vestibulo-visual conflict

You motor learn to reduce to ratio of eye to head movement of the VOR

52
Q

How long does it take for motor learning to occur.?
Is it retained?
What does being retained mean?

A

A few hours.
Yes it is retained meaning that even if the lights are turned off(no visual field) the eyes will still turn less that the head because it has learned to adjust the VOR response

53
Q

What does plasticity in motor learning depend on?

A

The integrity of the inferior olive and cerebellar cortex which appraise “expected” with “actual” movement

54
Q

The cerebellum continually regulates the neuronal activity of motor commands via what two loops?
What structures are involved in each loop?

A
  1. Excitatory loop through the deep cerebellar nuclei excited by mossy fibers
  2. Inhibitory loop via mossy fiber->granule cell parallel fiber->excite purkinje-> inhibit the deep cerebellar nuclei
55
Q

What is the strength of the excitatory cerebellum motor learning pathway?

A

(1- Pinhib)

56
Q

What is the motor learning system optimized for?

A
  1. Speed because the circuit can shape the motor command as it is being executed without feedback and delay
  2. Efficiency because the Strength of inhibition can be adjusted up or down by LTD or LTP to improve performance
57
Q

What neuronal trigger lets the motor learning inhibitory loop know to modify its synaptic strength?

A

Climbing fiber activity from the contralateral inferior olive

58
Q

How do LTD and LTP work in the motor learning loops?

A

LTD is increased when there is increase in climbing fiber activity because more purkinje will be exited and will inhibit the deep cerebellar nuclei

LTP is increased with decreased climbing fiber input

59
Q

If you lost the whole inhibitory loop for motor learning would you still have VOR?

A

Yes because the excitatory pathway still works, but if would not be regulated or able to adjust to changing stimuli and visual field/vestibular discrepancies

60
Q

If there was damage to the Vestibulocerebellum, what would you see?

A

Irregular Eye movements:

  1. Smooth tracking
  2. Fixed gaze due to loss of inhibitor projections to vestibular nuclei
  3. Nystagmus- gradual drift away from target, with rapid compensatory movements back toward the target

postural adjustments would be abnormal, affected proximal muscle groups because of Vermal component

Wide-based irregular gait (truncal ataxia)

Nausea and vomiting

61
Q

What would injury to the paravermal region of the spinocerebellum and lateral cerebellar regions cause?

A
  1. Loss of coordination in distal muscle groups
  2. Intention tremors
  3. overshooting specific targets (dysmetria)
  4. Impaired rapid alternating movements
  5. Loss of fine motor control
  6. Hypotonic bc of loss of Rubrospinal input
62
Q

Why might a person with a lateral cerebellar injury appear hypotonic (especially in the upper extremities)?

A

Input to the magnocellular portion of the red nucleus is lost and the Rubrospinal tract is what regulates truncal tone in the cervical region

63
Q

What side would you notice symptoms in a lateral cerebellar hemispheric lesion?

A

Ipsilaterally because the efferents go through the superior cerebellar peduncle to the contraltetal thalamus and red nucleus to the ipsilateral cortex.
Motor Signals in the cortex cross back in the medulla after traveling through the corticospinal tracts

Neuroscience Block 3 (20 decks)

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