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Y2 LCRS2 Neuroscience and Mental Health > Motor pathways: Cortical motor function, basal ganglia and cerebellum > Flashcards

Motor pathways: Cortical motor function, basal ganglia and cerebellum Flashcards

1
Q

What is the difference in function between the higher and lower cortical areas of the brain?

A

Higher areas program and coordinate tasks, lower order areas execute tasks

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2
Q

What is the pyramidal tract composed of?

A

Corticospinal tract

Corticobulbar tract

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3
Q

What makes up the extrapyramidal tract?

A

Cerebellum

Basal ganglia

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4
Q

What are lower motor neurons and upper motor neurons?

A
  • Lower motor neuron
    • Spinal cord, brainstem
  • Upper motor neuron
    • Corticospinal, corticobulbar
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5
Q

Where is the M1?

A

Pre-central gyrus anterior to the central sulcus

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6
Q

What is the function of M1?

A

Fine, discrete, precise voluntary movement

Provide descending signals to execute movement

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7
Q

Describe the layers of M1

A

6 layers

Layer 5 has Betz cells = very large pyramidal cells

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8
Q

Explain the mapping of M1 and the relevance to stroke

A

Somatotopic - Penfield’s homunculus

Not much representation of the trunk since musculature is minimal .

  • Stroke affecting MCA –> upper limb dysfunction
  • Stroke affecting ACA –> lower limb dysfunction
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9
Q

Recall the pathway taken by 90% of descending motor neurons

A

LATERAL CORTICOSPINAL TRACT

  • M1
  • internal capsule
  • cerebral peduncles in midbrain
  • not visible in pons because of transverse fibres
  • base of medulla in pyramids = decussation
  • lateral corticospinal tract
  • ventral horn
  • *synapse with alpha neuron*
  • ventral root
  • spinal nerve
  • musculature for voluntary movement
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10
Q

Recall the pathway taken by descending motor neurons that do not decussate in the medulla

A

Anterior corticospinal tract:

  • M1
  • internal capsule
  • cerebral peduncles
  • pyramids - 5% don’t cross and keep going iipsilaterally in the anterior corticospinal tract
  • anterior corticospinal tract
  • ventral horn
  • *synapse with alpha neuron*
  • *cross side*
  • ventral root
  • spinal nerve
  • AXIAL musculature - trunk and proximal parts of limbs
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11
Q

What is the main difference between the corticospinal and corticobulbar tracts?

A

Corticobulbar = CRANIAL nerves (nuclei in brainstem)

Corticospinal = spinal nerves

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12
Q

Recall the corticobulbar pathways.

A
  • Fibres descend from the “head” region of the motor cortex
  • Fibres pass through the genu of the internal capsule and down through brainstem
  • They then reach the hypoglossal nucleus on the contralateral side and its motor neruons send their axons to the tongue.
  • Anteriorly the medulla has three cranial nerves coming out of the lateral medulla -9,10 and 11
  • Cranial nerve 12 comes out between the pyramids and the olive.
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13
Q

Label:

A
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14
Q

What is the function of the premotor cortex and where is it located?

A

Anterior to M1, regulates externally cued movements and plans movements

e.g. seeing an apple and reaching out for it requires moving a body part relative to another body part (intra-personal space) and movement of the body in the environment (extra-personal space)

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15
Q

What is the role of the supplementary motor cortex? Recall 3

A
  1. Planning of complex movements
  2. Programming sequencing of movements
  3. Regulates internally driven movements e.g. speech mechanics

Becomes active when thinking about a movement before executing it.

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16
Q

Recall the 2 association motor cortices

A
  1. Posterior parietal
  2. Prefrontal
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17
Q

What is the function of each of the association motor cortices?

A
  1. PP = ensures movements are targeted accurately to objects in external space
  2. PF = selects appropriate movements for particular course of action
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18
Q

Recall 2 negative signs of an upper motor neuron lesion

A

Paresis - graded weakness of movements

Plegia (paralysis) - complete loss of muscle activity

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19
Q

Recall 5 positive signs of an upper motor neuron lesion

A
  1. Babinski’s sign
  2. Clonus - abn oscillatory muscle contraction
  3. Increased muscle tone (spasticity)
  4. Hyper-reflexia

Also apraxia

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20
Q

What is clonus?

A

Abonormal oscillatory muscle contraction

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21
Q

What are the most common causes of apraxia?

A

Stroke or dementia

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22
Q

Dysfunction of which lobes are most likely to result in apraxia?

A

Inferior parietal or frontal (premotor cortex, supplementary motor area)

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23
Q

What is apraxia?

A

Disorder of skilled movement

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24
Q

How does the presentation of a lower motor neuron lesion differ from that of an UMN lesion?

A
  1. Weakness, hypotonia and hyporeflexia
  2. Muscle atrophy
  3. Fasciculations
  4. Fibrillations - spon twitching of individual muscle fibres
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25
Q

What is a fasciculation?

A

Visible twitch due to motor unit damage (NB: fibrillations are ndivid muscle fibre twitches and are detected by needle EMG)

26
Q

By what other name is motor neuron disease known?

A

Amyotrophic lateral sclerosis

27
Q

Recall 6 upper motor neuron signs of ALS

A
  1. Increased muscle tone and spasticity (limbs and tongue)
  2. Brisk limb and jaw reflexes
  3. Babinski’s sign
  4. Dysarthria
  5. Dysphagia
  6. Loss of dexterity
28
Q

Recall 5 lower motor neuron signs of ALS

A
  1. Weakness
  2. Wasting
  3. Tongue fasciculations and wasting
  4. Nasal speech
  5. Dysphagia
29
Q

Recall the 8 key component structures of the basal ganglia(extrapyramidal).

A
  1. Caudate nucleus
  2. Lentiform nucleus (putamen + ext globus pallidus)
  3. Subthalamic nucleus
  4. Substantia nigra
  5. Ventral pallidum
  6. Claustrum
  7. Nucleus accumbens
  8. Nucleus basilis of Meynert
30
Q

What is the striatum of the BG made up of?

A

Caudate and lentiform nuclei

31
Q

What is the lentiform nucleus made up of?

A

Putamen and external globus pallidus

32
Q

How can neurosurgeons cure tremor in Parkinson’s patients?

A

Moddification of subthalamic nucleus

33
Q

What is the function of the nucleus accumbens?

A

Underlies reward and addiction behaviours

34
Q

What is the main function of the nucleus basilis of Meynert?

A

Memory

35
Q

Where is the caudate nucleus?

A

Lateral wall of lateral ventricle

36
Q

Recall 3 functions of the basal ganglia

A
  1. Elaborating associated movements e.g. changing facial expression to match emotions, swinging arms when walking
  2. Suppressing unwanted movements - moderating and coordinating movement
  3. Sequencing movements
37
Q

Recall the circuitry of the basal ganglia and state 3 conditions affecting it.

A
38
Q

Recall the progression of neuron breakdown in Huntingdon’s

A

GABAergic neuron breakdown in striatum then

Caudate nucleus

Then Putamen(/globus pallidus) in lentiform nucleus

39
Q

What sort of neurons are broken down in Parkinson’s?

A

Dopaminergic neurons in the substantia niagra which sends neurons to the striatum

40
Q

What is the black substance that makes up the substantia nigra?

A

Neuromelanin- released from dopaminergic cells

41
Q

Where is the substantia nigra?

A

Midbrain

42
Q

What is a characteristic sign of Parkinson’s on brain sections?

A

As you age the substantia niagra should get darker - if the dark line is missing then this is a sign of Parkinson’s

43
Q

Recall 5 presentations of Parkinson’s

A
  1. Bradykinesia - slowness of movements
  2. Hypomimic face - expressionless due to absense of movements that normally animate the face
  3. Akinesia - difficulty initiating movements
  4. Rigidity
  5. Tremor at rest
44
Q

Describe the characteristic tremor in Parkinson’s Disease.

A

“pin rolling tremor”

4-7Hz

Starts in one hand then spreads to other parts of body

45
Q

Describe the inheritance of Huntingdon’s disease

A
  • Chromosome 4
  • Autosomal dominant
  • CAG repeats - >35 = almost certain

Pathophysiology: degeneration of GABAergic neurons in striatum, caudate, putamen.

46
Q

What are chorea?

A

Rapid, jerky involuntary movements

47
Q

Describe the progression of chorea in Huntingdons’s disease

A

First affects hands and face and then legs and rest of body

48
Q

Recall 5 signs of Huntingdon’s

A
  1. Choreic movements
  2. Unsteady gait
  3. Speech impairment
  4. Dysphagia
  5. In later stages, cognitive decline and dementia
49
Q

Recall the 3 divisions of the cerebellum

A
  1. Vestibulocerebellum
  2. Spinocerebellum
  3. Cerebrocerebellum
50
Q

What is the main function of the vestibulocerebellum?

A
  1. Gait and posture regulation and equilibrium
  2. Coordination of head movements with eye movements
51
Q

What are the 3 main functions of the spinocerebellum?

A
  1. Speech coordination
  2. Coordination of limb movements
  3. Adjustment of muscle tone
52
Q

WHat are the 4 main functions of the cerebrocerebellum

A
  1. Coordination of skilled movements
  2. Cognitive function and attention
  3. Processing language
  4. Emotional control
53
Q

Recall 2 symptoms of vestibulocerebellar syndrome.

A
  1. Gait ataxia
  2. Tendency to fall

Usually caused by tumour.

54
Q

What is the most common cause of spinocerebellar syndrome?

A

Chronic alcoholism

55
Q

What are the symptoms of spinocerebellar syndrome?

A

Damage affects mainly legs, causes abnormal gait and stance (wide-based) (from chronic alcoholism)

56
Q

What are the symptoms of cerebrocelebellar/lateral cerebellar syndrome?

A

Arms mainly affected, skilled coordinated movements (tremor) and speech

57
Q

Recall 5 signs of cerebellar dysfunction

A
  1. Ataxia
  2. Dysmetria
  3. Intention tremor
  4. Dysdiadochokinesia
  5. Scanning speech
58
Q

What is ataxia?

A

Really drunken-looking gait

59
Q

What is dysmetria?

A

Inappropriate force and distance for targeted movements

60
Q

What is an intention tremor?

A

Tremor when asked to perform a motor command

61
Q

What is dysdiachokinesia?

A

Inability to perform rapidly alternating movements

62
Q

What is scanning speech and what causes it?

A

Staccato speech Causes by laryngeal muscle dysfunction in cerebellar syndromes

Y2 LCRS2 Neuroscience and Mental Health (17 decks)

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