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

Where is the M1?

A

Pre-central gyrus

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5
Q

What is the function of M1?

A

Fine, discrete, precise voluntary movement

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6
Q

Describe the layers of M1

A

6 layers

Layer 5 has Betz cells = very large pyramidal cells

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7
Q

Explain the mapping of M1 and the relevance to stroke

A

Somatotopic - Penfield’s homunculus
Stroke affecting MCA –> upper limb dysfunction
Stroke affecting ACA –> lower limb dysfunction

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8
Q

Recall the pathway taken by 90% of descending motor neurons

A
M1 
internal capsule
cerebral capsules
pyramids
decussation
lateral corticospinal tract
ventral horn
*synapse with alpha neuron*
ventral root
spinal nerve
musculature
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9
Q

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

A
M1 
internal capsule
cerebral capsules
pyramids
anterior corticospinal tract
ventral horn
*synapse with alpha neuron*
*cross side* 
ventral root
spinal nerve
AXIAL musculature
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10
Q

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

A
Corticobulbar = CRANIAL nerves
Corticospinal = spinal nerves
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11
Q

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

A

Anterior to M1, regulates externally cued movements

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12
Q

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

A
  1. Planning of complex movements
  2. Movement sequences
  3. Speech mechanics
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13
Q

Recall the 2 association motor cortices

A
  1. Posterior parietal

2. Prefrontal

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14
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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15
Q

Recall 2 negative signs of an upper motor neuron lesion

A

Paresis

Plegia

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16
Q

Recall 5 positive signs of an upper motor neuron lesion

A
  1. Babinski’s sign
  2. Clonus
  3. Increased muscle tone (spasticity)
  4. Hyper-reflexia
  5. Apraxia
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17
Q

What is clonus?

A

Abonormal oscillatory muscle contraction

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18
Q

What are the most common causes of apraxia?

A

Stroke or dementia

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19
Q

Dysfunction of which lobes are most likely to result in apraxia

A

Inferior parietal or frontal

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20
Q

What is apraxia?

A

Disorder of skilled movement

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21
Q

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

A
  1. Decreased tone and reflex speed
  2. Muscle atrophy
  3. Fasciculations
  4. Fibrillations
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22
Q

What is a fasciculation?

A

Visible twitch due to motor unit damage

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23
Q

By what other name is motor neuron disease known?

A

Amyotrophic lateral sclerosis

24
Q

Recall 6 upper motor neuron signs of ALS

A
  1. Increased muscle tone and spasticity
  2. Hyper-reflexIia
  3. Babinski’s sign
  4. Dysarthria
  5. Dysphagia
  6. Loss of dexterity
25
Q

Recall 5 lower motor neuron signs of ALS

A
  1. Myopathy
  2. Atrophy
  3. Tongue fasciculations
  4. Nasal speech
  5. Dysphagia
26
Q

Recall the 8 key component structures of the basal ganglia

A
  1. Caudate nucleus
  2. Lentiform nucleus
  3. Subthalamic nucleus
  4. Substantia nigra
  5. Ventral pallidum
  6. Claustrum
  7. Nucleus accumbens
  8. Nucleus basilis of Meynert
27
Q

What is the striatum of the BG made up of?

A

Caudate and lentiform nuclei

28
Q

What is the lentiform nucleus made up of?

A

Putamen and external globus pallidus

29
Q

How can neurosurgeons cure tremor in Parkinson’s patients?

A

Moddification of subthalamic nucleus

30
Q

What is the function of the nucleus accumbens?

A

Underlies reward and addiction behaviours

31
Q

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

A

Memory

32
Q

Where is the caudate nucleus?

A

Lateral wall of lateral ventricle

33
Q

Recall 3 functions of the basal ganglia

A
  1. Changing facial expression to match emotions
  2. Suppressing unwanted movements
  3. Sequencing movements
34
Q

Recall the progression of neuron breakdown in Huntingdon’s

A

GABAergic neuron breakdown
First caudate nucleus
Second GP in LN

35
Q

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

A

Dopaminergic

36
Q

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

A

Neuromelanin- released from dopaminergic cells

37
Q

Where is the substantia nigra?

A

Midbrain

38
Q

Recall 6 presentations of Parkinson’s

A
  1. Bradykinesia
  2. Hypomimic face
  3. Micrographia
  4. Akinesia
  5. Rigidity
  6. Tremor at rest
39
Q

At what frequency is a Parkinson’s tremor?

A

4-7Hz

40
Q

Describe the inheritance of Huntingdon’s disease

A

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

41
Q

What are chorea?

A

Rapid, jerky involuntary movements

42
Q

Describe the progression of chorea in Huntingdons’s disease

A

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

43
Q

Recall 5 signs of Huntingdon’s

A
  1. Chorea
  2. Unsteady gait
  3. Speech impairment
  4. Dysphagia
  5. In later stages, cognitive decline and dementia
44
Q

Recall the 3 divisions of the cerebellum

A
  1. Vestibulocerebellum
  2. Spinocerebellum
  3. Cerebrocerebellum
45
Q

What is the main function of the vestibulocerebellum?

A

Gait and posture regulation

46
Q

What are the 3 main functions of the spinocerebellum?

A

Speech coordination
Coordination of limb movements
Adjustment of muscle tone

47
Q

WHat are the 4 main functions of the cerebrocerebellum

A
  1. Language processing
  2. Coordination of skilled movements
  3. Motor learning
  4. Some emotional control
48
Q

Recall 2 symptoms of vestibular disease

A

Gait ataxia

Tendency to fall

49
Q

What is the most common cause of spinocerebellar syndrome?

A

Chronic alcoholism

50
Q

Recall 5 signs of cerebellar dysfunction

A
  1. Ataxia
  2. Dysmetria
  3. Intention tremor
  4. Dysdiadochokinesia
  5. Scanning speech
51
Q

What is ataxia?

A

Really drunken-looking gait

52
Q

What is dysmetria?

A

Inappropriate force and distance for targeted movements

53
Q

What is an intention tremor?

A

Tremor when asked to perform a motor command

54
Q

What is dysdiachokinesia?

A

Inability to perform rapidly alternating movements

55
Q

What is scanning speech and what causes it?

A

Staccato speech

Causes by laryngeal muscle dysfunction in cerebellar syndromes