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PHTH 7303 Neuro > Exam 3 Week 12 pp 7-9 3 sections of cerebellum > Flashcards

Exam 3 Week 12 pp 7-9 3 sections of cerebellum Flashcards

1
Q

Vestibular afferents project to _____

A

cortex of vestibulocerebellum and to the fastigial nucleus through the inferior cerebellar peduncle

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2
Q

Where do primary vestibular afferents start from?

A

direct from ispilateral CN VIII

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3
Q

Where do secondary vestibular afferents start from?

A

from ipsilateral vestibular nuclei

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4
Q

Why do I care about vestibular afferents?

A

because they influence distribution of tone in limbs, trunk, neck, and extraocular eye muscles

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5
Q

How does the visual systems project to vestibulocerebellum?

A

indirectly to vestibulocerebellum through climbing fibers of the inferior olivary nucleus

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6
Q

Function of visual system input

A

Assists in regulating the vestibular ocular reflex (VOR)

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7
Q

What are the two places in the brain stem that receive outputs from the vestibulocerebellum?

A
  1. Vestibular nuclei
    • From vestibular nuclei to influence extraocular motor neurons via MLF
    • From vestibular nuclei to influence body and limb tone and responses via the vestibulospinal tracts
  2. –Reticular formation
    • Descending fibers of reticulospinal tracts
    • Ascending fibers to extraocular motor nuclei
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8
Q

Where does the vestibulocerebellum have outputs?

A

to the brainstem Vestibular nuclei

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9
Q

Purpose of the projections through the vestibular nuclei: (2)

A
  1. influence extraocular motor neurons via the medial longitudinal fasciculus
  2. play a role to influence body and limb tone and responses via the vestibulospinal tracts
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10
Q

Second location where vestibulocerebellum outputs to the brainstem end and why

A

-nuclei of the Reticular formation -These nuclei send both Descending fibers forming the reticulospinal tracts and Ascending fibers to extraocular motor nuclei

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11
Q

Functions of the vestibulocerebellum (Flocculonodular lobe): (3)

A
  1. Balance in sitting, standing & gait
  2. Plasticity of vestibulo-ocular reflex
  3. Nodule function related to sensitivity to motion sickness (ablated this makes subject immune to motion sickness
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12
Q

Nyanduk’s favorite animal

A

monkeys

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13
Q

major role of spinocerebellum

A

comparator -defined on interwebs as a device for comparing a measurable property or thing with a reference or standard. an electronic circuit for comparing two electrical signals. something used as a standard for comparison.

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14
Q

So what makes spinocerebellum a comparator? (3)

A
  1. Information about intended movement is sent to the cerebellum – efference copy, a copy of the outgoing command to move – Feed forward signal from inferior olive
  2. Patterns of peripheral proprioceptor discharge are also sent to the cerebellum - feedback
  3. Cerebellum constantly updates movement as it is evolving
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15
Q

Functions of Vermis (2)

A
  • Movement coordination of axial & proximal limb musculature
  • Probable regulation of postural muscle tone
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16
Q

Where do the inputs from vermis come from? (types of input)

A

Proprioception, Vision & Vestibular sensory systems

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17
Q

What happens if spinal proprioceptive input to vermis is damaged? (4)

A

Damage results in sensory ataxia:

  1. Ataxic symptoms without visual support
  2. Increased postural sway
  3. Difficulty in standing with narrow base of support and eyes closed (Romberg sign)
  4. Uncoordinated gait
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18
Q

How is body mapped on cerebellum?

A

somatotopically mapped on the cerebellum with separate somatopic maps on anterior and posterior lobes of cerebellum

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19
Q

How many homunculi are on the cerebellum?

A

two

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20
Q

How are homunculi distributed?

A

Two homunculi are inverted images of one another Neck & trunk are vermal & extremities paravermal

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21
Q

Afferent tracts of the Spinocerebellum (5)

A
  1. Dorsal spinocerebellar tract (DSCT)
  2. Cuneocerebellar tract (CCT)
  3. Ventral spinocerebellar tract (VSCT)
  4. Rostral spinocerebellar tract (RSCT)
  5. Trigeminocerebellar projections
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22
Q

Pathway of Dorsal spinocerebellar tract (DSCT)

A
  • Arises from cells of Nucleus dorsalis (Clarke’s) in spinal segments T1 to L2 or L3
  • Axons rise ipsilaterally in dorsal lateral funiculus to enter thru inferior peduncle -Axons end in areas representing LE & trunk in anterior & posterior lobes
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23
Q

Pathway of Ventral spinocerebellar tract (VSCT)

A
  • Arises from nuclei scattered in based of dorsal horn -Axons decussate to rise in peripheral lateral funiculus just ventral to contralateral DSCT
  • Axons ascend thru medulla & pons to decussate again and enter thru superior cerebellar peduncle
  • Axons end in LE representation of anterior lobe and paramedian lobule
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24
Q

What type of activity do Ventral spinocerebellar tract (VSCT) and Dorsal spinocerebellar tract (DSCT) have in common?

A

phasic activity during gait stepping cycle

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25
Q

Section dorsal roots affects which tract during phasic activity

A

Dorsal spinocerebellar tract (DSCT) only

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26
Q

What happens to phasic gait cycle pattern if dorsal roots were cut

A

Ventral spinocerebellar tract continues its phasic gait cycle pattern

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27
Q

DSCT neurons of the Clarke’s column are driven by______

A

proprioceptive afferents – unconscious proprioception

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28
Q

VSCT cells at the base of the dorsal horn driven by__________

A

descending motor commands – efferent copy

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29
Q

Pathway of Cuneocerebellar tract (CCT)

A
  • Primary afferents from upper extremity proprioceptors ascend in fasciculus cuneatus to end in accessory (lateral) cuneate nucleus (ACN) of caudal medulla
  • CCT axons from ACN enter inferior cerebellar peduncle innervating areas representing UE
  • CCT axons from ACN carry information from muscle spindles, GTOs & joints
  • Cutaneous input enters cerebellum from neurons in main cuneate nucleus – providing proprioceptive input from hands and fingers
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30
Q

Pathway of Rostral spinocerebellar tract (RSCT)

A
  • Arise from cells scattered thru cervical segments
  • Rise ipsilaterally to enter thru inferior cerebellar peduncle but evidence for contralaterally rising axons which enter thru superior cerebellar peduncle
  • End of both LE & UE representations of ipsilateral anterior & posterior lobes of cerebellum
31
Q

Pathway of Trigeminocerebellar tract (TCT)

A
  • Cells in mesencephalic, chief sensory and spinal tract nuclei of CN V all contribute to these projections
  • Some fibers enter thru superior and others thru inferior cerebellar peduncles
  • TCT axons end ipsilaterally in the posterior lobe area with face representation
32
Q

Other inputs to cerebellum (2)

A

Visual & auditory inputs

33
Q

Where do visual & auditory inputs in cerebellum end?

A

End in same region as face representation in posterior lobe

34
Q

How do visual inputs function?

A

provide sense of verticality & horizontality from the visual space for maintenance of upright stance

35
Q

In what ways does cerebellum participate in cognitive functions related to hearing? (6)

A
  1. Speech generation
  2. Auditory processing
  3. Auditory memory
  4. Abstract reasoning & solution of problems
  5. Sensorial discrimination & information processing
  6. Language processing & linguistic operations
36
Q

Spinocerebellum outputs (nuclei)

A

fastigial and interposed nuclear outputs

37
Q

Fastigial outputs: what three places does the vermis project to?

A
  1. Vestibular Nuclei
  2. Reticular formation nuclei
  3. Thalamus: ventral lateral (VA) nucleus
38
Q

What do fastigial nucleus outputs include? (3)

A

Vermal outputs to vestibular & reticular nuclei

(and ventrolateral thalamic nucleus)

39
Q

How do vermal outputs to vestibular & reticular nuclei project (unilateraly or bilaterally) and why?

A

project bilaterally to control axial muscles

40
Q

Where else (besides vestibular and reticular nuclei) do vermal outputs project?

A

to ventral lateral nucleus of the thalamus

41
Q

How do fastigial outputs from spinocerebellum function? (2)

A
  • Most feel that these function in control of proximal musculature during movement
  • Providing proximal stability for distal mobility
42
Q

What make up the interposed nucleus?

A

Globose and emboliform nuclei

43
Q

Two types of fibers of the globose and emboliform nuclei

A

Cerebellorubral fibers Cerebellothalamic fibers

44
Q

Pathway of Cerebellothalamic fibers

A

-globose and emboliform nuclei axons exit & decussate in superior cerebellar peduncle -most ending in the VL nucleus of thalamus which in turn projects to motor cortex

45
Q

Pathway of Cerebellorubral fibers

A

-globose and emboliform nuclei axons exit & decussate in superior cerebellar peduncle -Terminate in the magnocellular part of red nucleus. These outputs appear to activate rubrospinal pathways

46
Q

Purpose of Globose and emboliform nuclei

A

Globose and emboliform nuclei pathways to both the red nucleus and through the thalamus to the motor cortex are involved in fine motor control of the upper extremity

47
Q

What occurs if damage to Globose and emboliform nuclei?

A

Damage to these areas produces a 3-5 Hz Intention tremor during reaching tasks. But there is no similar effect of damage on gait or standing balance

48
Q

Role of Pontocerebellum (2)

A
  • Role in the governance of voluntary movement and motor learning
  • Role in timing of muscle activation (and inactivation), as well as influencing the duration of muscle contraction
49
Q

Does Pontocerebellum receive projections from peripheral receptors?

A

No

50
Q

Where do Afferent projections to the neocerebellum originate?

A

originate in the motor and association cortices of the cerebrum via cortico-pontocerebellar projections

51
Q

Where do Cortico-pontocerebellar projections travel? (6)

A
  1. -Descend from motor association cortex thru internal capsule & medial third of cerebral peduncle
  2. -End on neurons of pontine nuclei
  3. -Pontine nuclei axons decussate to enter thru contralateral middle cerebellar peduncle
  4. -Mossy fibers end on granule cells of lateral cerebellar cortex
  5. -Mossy fiber collaterals end on neurons in dentate nucleus
  6. -Carries information that cerebellum uses for movement initiation & execution
52
Q

What do lesions of Cortico-pontocerebellartract & pontine nuclei result in?

A

contralateral deficits in arm & leg coordination

53
Q

What does a lesion of the middle cerebellar peduncle results in?

A

ipsilateral deficits in arm & leg coordination

54
Q

After pontocerebellum cortex project to the dentate nuclei, where do projections travel?

A

project out via the superior cerebellar peduncle to: Contralateral red nucleus & Contralateral VL thalamus

55
Q

Where do dentate projections to red nucleus end?

A

end on Parvocellular neurons which project to inferior olivary nucleus. These neurons then project back into the cerebellum providing Regulatory feedback to the cerebellum

56
Q

What happens to dentate projections to VL nucleus of thalamus?

A

project to motor & premotor cortex whch produce Direct and indirect actions on UMN via corticospinal pathways & corticobulbar pathways

57
Q

What happens when dentate nucleus is damaged?

A

Movement initiation & voluntary execution of the movement is delayed

58
Q

What do the resulting impairments due to dentate nucleus damage suggest?

A

Suggests that dentate projections to motor cortex via VL nucleus of thalamus are essential for the initial activation of corticospinal neurons at the beginning of a movement

59
Q

What results when damage to the pontocerebellum produces delay of excitatory output from the motor cortex

A

results in a corresponding delay in muscle contraction

60
Q

When damage to pontocerebellum produces delay in agonist and antagonist contraction, what also happens?

A

Reciprocal pattern of activation in agonists and antagonists that accompanies many movements is dramatically disrupted

61
Q

Thinking about the pontocerebellum, what happens with damage that involves only the cerebellar cortex?

A

rarely results in permanent motor deficits

62
Q

What happens if there is damage to both deep nuclei and the cerebellar cortex?

A

Damage to both cortex & nuclei or to nuclei alone results in a wide range of motor problems

63
Q

Unilateral lesions of the cerebellum produce ________

A

ipsilateral deficits

64
Q

Why do unilateral lesions to cerebellum produce ipsilateral deficits?

A

Right dentate and interposed nuclei influence the left motor cortex and red nucleus and projections of the Left motor cortex & red nucleus project to the right side of the spinal cord. So a lesion in the cerebellum on the right results in deficits on the right side of the body

65
Q

What is the results with lesions of the lateral cerebellum?

A
  • deterioration of coordinated movement (movement decomposition) or dyssynergia
  • This deficit consists of the breakdown of movement into its individual component parts
  • Symptoms: hypotonia Ataxia Dysarthria Ocular motor coordination defects Dysmetria Intention tremor Dysdiadochokinesia
66
Q

What is dysmetria?

A

past pointing when pointing at stationary or moving objects

67
Q

Characteristics of Ataxia

A

incoordinated limb movement Unsteady gait Tendency to lean or fall to the side of the lesion

68
Q

Hypotonia

A

decrease in muscle tone & in deep tendon reflexes

69
Q

dyssynergia

A

lack of harmonious association of its various components; usually used to describe abnormalities of movement caused by cerebellar disorders.

70
Q

Dysdiadochokinesia

A

awkward performance of rapid alternating movements & also manifested by inability to perform repeated rhythmic movements

71
Q

Intention tremor

A

oscillation of limb as target is approached - occurs with performance of a voluntary movement

72
Q

Characteristics of Sensory ataxia (4)

A
  1. Disruption of proprioceptive afferents into the cerebellum
  2. Near-normal coordination when the movement in question is visually observed by the patient
  3. Marked worsening of coordination when the eyes are shut
  4. Positive Romberg sign & problem walking in dark
73
Q

Characteristics of Motor Ataxia (2)

A
  1. Damage to the cerebellum
  2. Ataxia symptoms with or without vision

PHTH 7303 Neuro (89 decks)

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