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Brain and Behavior > 6.1.1 Cerebellum > Flashcards

6.1.1 Cerebellum Flashcards

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1
Q

What are the characteristics of the Purkinje Cell?

A

Primary Output

Form inhibitory, GABA-ergic synapses

Have a high tonic firing rate

Cell bodies in Purkinje cell layer

Dendrites fan out with axons projecting ipsilaterally to deep cerebellar nuclei (spinocerebellum, cerebrocerebellum) as well as vestibular nucleus cells (vestibulocerebellum)

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2
Q

What are adiadochokinesis associated with lesions of the Cerebrocerebellum?

A
  • inability to make rapid alternating movements
  • Clinically: rapid pronation/supination of hands
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3
Q

The purkinje cell is?

A

inhibitory!

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4
Q

What is the Cerebellar Circuit for canceling the VOR?

A
  • Collaterals of CN VIII enter the cerebellum as mossy fibers
  • Mossy fibers excite granule cells
  • Granule cells bifurcate into parallel fibers
  • Parallel fibers excite Purkinje cells
  • Purkinje cells inhibit vestibular nucleus cells
  • Cancels the opposing inhibitory input from CN VIII afferents

-Result: no VOR

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5
Q

Describe the somatotopic organization of the Cerebellum.

A

Spinal input to the paleocerebellum is somatotopically organized in two representations

  1. Anterior Lobe: head is oriented posteriorly
  2. Posterior Lobe: head is oriented anteriorly

Somatotopy is also retained with muscle control

  1. Vermis: controls coordination/tone of the trunk
  2. Cerebellar Hemispheres: control coordination/tone of the limbs
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6
Q

What are the key points of the VOR?

A

Sinusoidal head rotation modulates 8th nerve afferent activity in a sinusoidal pattern. For example, head acceleration to the right activates 8th nerve afferents on the right.

This activity produces a proportional sinusoidal modulation of the firing rate of vestibular nuclear cells.

This activity is imposed on oculomotoneurons to produce an eye movement equal in magnitude but opposite in direction to the head movement.

The circuit through the cerebellum is switched off.

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7
Q

Does the Cerebellum have roles in emotion, intellect, sensory information or origination of movement?

A

NO

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8
Q

Draw out the diagram for the feedforward model of Motor Control.

A
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9
Q

What is the pathway for the initiation and execution of movement?

A
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10
Q

What are the anatomical components and function of the Vestibulocerebellum?

A

Anatomical Components: Nodulus of the vermis and the flanking flocculus on each side

Function: balance and eye movements (including control of VOR)

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11
Q

What are the characteristics of normal VOR?

A

Use: maintain fixation on a stationary object by moving the eyes in the opposite direction relative to head movement (acceleration)

No fluctuation in firing of purkinje cells

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12
Q

Inferior cerebellar peduncle receives efferent input from?

A

efferents from vestibular nuclei

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13
Q

Inferior cerebellar puduncles contain fibers from what tracts?

A

contains fibers from dorsal spinocerebellar tracts and cuneocerebellar tract

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14
Q

Superior cerebellar peduncle contains?

A

mostly efferent fibers, sending impulses to thalamus and spinal cord, with relays in the red nuclei; afferent fibers from the ventral spinocerebellar tract enter here

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15
Q

Describe the functions of the Vestibulocerebellum.

A

Coordinating Center for Vestibulo-postural Reflexes

In general terms, the cerebellum adds fine tuning to vestibulo-postural reflexes to ensure correct amplitude, strength and range of movement

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16
Q

What is the anatomical components and function of the Spinocerebellum?

A

Anatomical Components: Rest of vermis and adjacent medial portions of hemispheres

Function: motor execution (including error correction)

Vermis: controls axial and proximal muscles

Hemispheres: controls distal muscles

17
Q

Describe the Purkinje cell response to climbing fibers vs mossy fibers?

A
18
Q

Why would there ataxia associated with lesions of the Cerebrocerebellum?

A

lack of coordination of movements

19
Q

What is decomposition of movement associated with lesions of the Cerebrocerebellum?

A
  • fractioned movements during complex actions
  • Loss of smooth trajectory due to degradation in movement programming
20
Q

Cerebellar lesions affect what side of the body?

A

Ipsilateral side

21
Q

Cerebellar white matter contains?

A

four paired deep cerebellar nuclei:

fastigial

globose

emboliform

dentate

22
Q

What are symptoms of damage to Vestibulocerebellum?

A

nystagmus, dysequilibrium, wavering ataxic gate

Difficulty maintaining balance ⇒ broad based gait

23
Q

Middle cerebellar peduncle contains fibers from?

A

contralateral pontine nuclei (info from cortex)

24
Q

What are the covered portions?

A
25
Q

What is intention tremor or action tremor associated with lesions of the Cerebrocerebellum?

A
  • high frequency tremor associated with voluntary movements
  • Particularly prominent at the end of movements
  • Clinically: finger to nose test
26
Q

What are the functions of the Cerebellum?

A
  • Center for coordinating many different types of movements and reflexes
  • adding fine-tuning to reflexes and voluntary movements
  • Make corrections to movements in terms of strength and timing
  • Can switch reflexes on and off as well as modifying the strength of reflexes
27
Q

What are the key points of suppression of the VOR?

A

Head movement still produces activation of the right horizontal semicircular canal 8th nerve afferents and this activity is transmitted to the brainstem.

The circuit involving 8th nerve afferent collaterals to the cerebellum is switched on producing a proportional sinusoidal modulation of Purkinje cells.

The inhibitory activity of Purkinje cells impinges on cerebellar nuclear cells almost simultaneous with the excitatory activity arriving from 8th nerve afferents.

These two inputs to the vestibular nucleus cell cancel each other, that is, inhibitory potentials from Purkinje cells cancel excitatory potentials from 8th nerve afferents.

The firing rate of vestibular nucleus cells remains unchanged (unmodulated).

28
Q

Why would there hypotonia associated with lesions of the Cerebrocerebellum?

A

-decrease in gamma motoneuron activity

29
Q

What is the flocculus of the cerebellum?

A

small posterior lobe connected to the rest of the cerebellum via nodule of the vermis

30
Q

What are the two factors involved in the spinocerebellum that allows it to act as comparator in the ongoing correction of movements?

A
  1. Monitoring the course of a movement –––> spinocerebellar tracts
  2. Monitoring the command for movement (i.e., the desired movement) –––> pontocerebellar input from motor cortex.
  3. Issuing an error correction based on the difference between the intended and actual movement
31
Q

What is the importance of the climbing fibers?

A

Input

Originate from inferior olivary nucleus

Make excitatory synapses with small number of purkinje cells

32
Q

What are mossy fibers?

A

Make excitatory synapses with granule cells and then parallel fibers from these granule cells then make up to 10,000 synapses with Purkinjes

Originate from pontine nuclei and spinocerebellar tracts

33
Q

What are symptoms of lesions of the cerebrocerebellum?

A
34
Q

What is the use of suppression of the VOR by Vestibulocerebellum?

A

maintain fixation on a moving object by keeping eyes stationary in head as it moves

35
Q

What are the characteristics of the Granule Cell?

A

Indirect Output

Form excitatory, Glutaminergic synapses

Only excitatory neurons in the cerebellar CORTEX

Cell bodies in Granule cell layer

Send axons upward into the molecular cell layer where they bifurcate to form parallel fibers

Parallel fibers run perpendicular through Purkinje cell dendrites

36
Q

What is the Vermis of the cerebellum?

A

midline portion that separates two lateral hemispheres (which each contain an anterior and posterior lobe)

37
Q

What are the anatomical components and function of the Cerebrocerebellum?

A

Anatomical Components: Lateral portions of the cerebellar hemispheres

Function: motor planning and programming

38
Q

What is the function of the Cerebrocerebellum?

A
  • General function: initiation and programming of movement
  • Programming requires information related to what muscles should contract, what force is need, and what the timing/duration of this force should be
  • Programming is especially important for fast movements where there is inadequate time for effective modification of movement via afferent feedback
39
Q

Lesion of the vestibulocerebellum will cause?

A

Brain and Behavior (89 decks)

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