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1B Neurology & Neuroscience > Motor cortical control > Flashcards

Motor cortical control Flashcards

1
Q

what are the main principles of motor cortical control?

A
  • Hierarchical organisation
    • Higher order areas of hierarchy involved in more complex tasks
  • Functional segregation
    • Motor system organised in number of different areas that control different aspects of movement
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2
Q

what does the brain stem do?

A

passes commands from the cortex to the spinal cord

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3
Q

what does the motor cortex do?

A

receives information from other cortical areas and sends commands to the thalamus and brainstem

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4
Q

what do the cerebelllum and basal ganglia do?

A

adjust the commands received from other parts of the motos system

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5
Q

what are the major descending motor tracts?

A

pyramidal tracts

extrapyramidal tracts

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6
Q

what are the pyramidal tracts?

A
  1. Corticospinal
  2. Corticobulbar
  3. Pass through pyramids of medulla
  4. Motor cortex to spinal cord or cranial nerve nuclei via brainstem
  5. Voluntary movements of body and face
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7
Q

what are the extrapyramidal tracts?

A
  1. Vestibulospinal
  2. Tectospinal
  3. Reticulospinal
  4. Rubrospinal
  5. Do not pass through pyramids
  6. Brainstem nuclei to spinal cord
  7. Involuntary (automatic) movements for balance, posture and locomotion
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8
Q

where is the primary motor cortex and what is its function?

A
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9
Q

where is the pre-motor area and what does it do?

A
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10
Q

where is the supplementary motor area and what does it do?

A
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11
Q

how do signals travel down the corticospinal tract?

A
  1. upper motor neuron signals travel to cerebral peduncle in midbrain
  2. travel into medullar to pyramids where they decussate (90%)
  3. decussated fibres travel down lateral corticospinal tract
  4. non-decussated fibres travel ipsilaterally down anterior corticospinal tract
  5. to lower motor neuron
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12
Q

what do the fibres from anterior corticospinal tract control?

A

trunk muscles

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13
Q

what do fibres from lateral corticospinal tract control?

A

limb muscles

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14
Q

how are the brain areas dedicated to processing anatomical divisions of the body?

A

motor homunculus

somatotopic representation

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15
Q

what is the function of the corticobulbar tract?

A

principle motor pathway for voluntary movements of the face (and neck)

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16
Q

what nerves does the corticobulbar tract act on?

A

The corticobulbar tract directly innervates the nuclei for cranial nerves:

V - Trigeminal- muscles for mastication

VII- Facial- muscles of the face

XI- Accessory- sternocleidomastoid and trapezius

XII- Hypoglossal- muscles of the tongue

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17
Q

what is the function of the vestibulospinal tract?

A

stabilise head movements, or as head moves coordinate head movements with eye movements

mediate postural adjustment

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18
Q

what is the function of the reticulospinal tract?

A

most primitive descending tract

from medullar to pons

changes in muscle tone associated with voluntary movements

postural stability

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19
Q

where does the tectospinal tract run and what are its functions?

A

from superior colliculus of midbrain

orientation of head and neck during eye movements

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20
Q

where does rubrospinal tract run and what are its functions?

A

from red nucleus of midbrain

in humans mainly taken over by corticospinal tracts

innervate lower motor neurons of flexors of the upper limb

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21
Q

what are the negative signs of upper motor neuron lesions?

A
  • Loss voluntary motor function
  • Paresis- graded weakness of movements
  • Paralysis (plegia) – complete loss voluntary muscle activity
22
Q

what are the positive signs of upper motor neuron lesions?

A
  • Increased abnormal motor function due to loss of inhibitory descending inputs
  • Spasticity- increased muscle tone
  • Hyper-reflexia- exaggerated reflexes
  • Clonus- abnormal oscillatory muscle contraction
  • Babinski’s sign
23
Q

a defect in what areas cause apraxia?

A
  • Lesions of inferior parietal lobe, frontal lobe (premotor cortex, supplementary motor area-SMA)
  • Any disease of these areas can cause apraxia (stroke and dementia most common)
24
Q

what is apraxia?

A

disorder of skilled movements

patients not paretic but lost information about how perform skilled movements

25
Q

what are the symptoms of lower motor neuron lesions?

A
  • Weakness
  • Hypotonia
  • Hyporeflexia
  • Muscle atrophy
  • Fasciculations
    • Damaged motor units produce spontaneous action potential= twitch visible
  • Fibrillations
    • Spontaneous twitching individual muscle fibres, recorded during needle electromyography exam
26
Q

what is motor neurone disease?

A

progressive neurodegenerative disorder of motor system

spectrum of disorder

also known as amyotrophic lateral sclerosis (ALS)

affects upper and lower motor neurons

27
Q

what are the upper motor neuron signs?

A
  • Spasticity
  • Babinskis sign
  • Loss dexterity
  • Dysarthria (diff speaking)
  • Dysphagia (diff swallowing)
  • Brisk limbs and jaw reflexes
28
Q

what are the lower motor neuron signs?

A
  • Weakness
  • Muscle wasting
  • Tongue fasciculation + wasting
  • Nasal speech
  • dysphagia
29
Q

what is the structure of the basal ganglia?

A

cluster of subcortical nuclei

  • caudate nucleus
  • lentiform nucleus (putamen + external globe pallidus)

together the caudate and putamen are known as the striatum

  • nucleus acumbens
  • subthalamic nuclei
  • substantia nigra (Midbrain)
  • ventral pallidum, claustrum, nucleus basalis (of Meynert)
30
Q

what is the function of basal ganglia?

A

decision to move

elaborating associated movements (e.g swinging arms when walking; changing facial expressions to match emotions)

moderative and coordinating movement (suppressing unwanted movements)

performing movements in order

31
Q

what is the development structure of the basal ganglia?

A
32
Q

what is the circuitry of the basal ganglia?

A
33
Q

what is parkinson’s disease?

A
  • degeneration dopaminergic neurons that originate in substantia nigra and project to striatum
34
Q

what are the effects of Parkinson’s disease?

A
  • bradykinesia (slowness small movements)
  • hypomimic face- expressionless, masklike
  • akinesia- difficulty in initiation movements as cannot initiale movement internally
  • rigidity- increased muscle tone, causing resistance to externally imposed join movements
  • tremor at rest- 4-7 Hz, starts in one hand (pill rolling tremor) and spreads to other parts body
35
Q

what is Huntington’s disease?

A
  • degeneration of GABAergic neurons in striatum, caudate and then putamen
  • genetic neurodegenerative disorder
  • chromosome 4, autosomal dominant, CAG repeat
36
Q

what are the effects of Huntington’s disease?

A
  • choreic- movements rapid jerky involuntary
  • speech impairment
  • dysphagia
  • unsteady gait
  • later stages= cognitive decline and dementia
37
Q

what is ballism caused by?

A

usually from strokes affecting subthalamic nuclei

38
Q

what are the effects of ballism?

A

sudden uncontrolled flinging of extremities

occurs contralaterally

39
Q

where is the cerebellum located?

A

posterior cranial fossa

separated from cerebellum above and below by tentorium cerebelli

40
Q

what are the functional divisions of the cerebellum?

A

vestibulocerebellum

spinocerebellum

cerebrocerebellum

41
Q

what is the vestibulocerebellum responsible for?

A
  • Regulation gait, posture and equilibrium
  • Coordination head movement with eye movements
42
Q

what are the effects of damage to the vestibulocerebellum?

A
  • Damage (tumour)= syndrome similar to vestibular disease
    • Gait ataxia, tendency to fall even when sitting with eyes open
43
Q

what is the spinocerebellum responsible for?

A
  • Coordination speech, adjustment muscle tone
  • Coordination limb movements
44
Q

what does damage to the spinal cerebellum cause?

A
  • Damage affects mainly legs- abnormal gait and stance (degen + atrophy assoc with chronic alcoholism)
45
Q

what are the functions of the cerebrocerebellum?

A
  • Coordination skilled movements
  • Cognitive function, attention, processing language
  • Emotional control
46
Q

what does damage to the cerebrocerebellum cause?

A
  • Damage affect mainly arms/ skilled coordinated movements (tremor) and speech
47
Q

what are the main signs of cerebellar dysfunction?

A

apparent only on movement

  1. ataxia
  2. dysmetria
  3. intention tremor
  4. dysdiadochokinesia
  5. scanning speech
48
Q

what is ataxia?

A

general impairments in movement coordination and accuracy

disturbances of posture or gait: wide biased, staggering gait

49
Q

what is dysmetria?

A

inappropriate force and distance for target-directed movements (knocking over a cup rather than grabbing it)

50
Q

what is intention tremor?

A

increasingly oscillatory trajectory of a limb in a target-directed movement (nose-finger tracking)

51
Q

what is dysdiadochokinesia?

A

inability to perform rapidly alternating movements (rapidly pronating and supinating hands and forearms)

52
Q

what is scanning speech

A

staccato due to impaired coordination of speech muscles

1B Neurology & Neuroscience (14 decks)

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