Cerebral motor control Flashcards

1
Q

What is the definition of functional segregation?

A

Different areas that control particular aspects of movements

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2
Q

What type of tracts are the corticospinal and corticobulbar tracts?

A

Pyramidal tracts (major descending)

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3
Q

What is the corticospinal tract responsible for?

A

The corticospinal tract is a motor pathway that carries efferent information from the cerebral cortex to the spinal cord. It is responsible for the voluntary movements of the limbs and trunk.

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4
Q

Where are the first order neurones located in terms of the corticospinal tract?

A

Primary motor cortex

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5
Q

What is the function performed by the corticobulbar tract?

A

Provides voluntary movements of body and face

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6
Q

What are the four types of extrapyramidal tracts?

A

1) Vestibulospinal
2) Tectospinal
3) Reticulospinal
4) Rubrospinal

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7
Q

Where is the primary motor cortex located?

A

Resides within the precentral gyrus anterior to the central sulcus.

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8
Q

What is the function performed by the primary motor cortex?

A

Such a cortex is responsible for controlling fine, discrete, precise voluntary movements and transmits descending signals to execute movements.

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9
Q

What is the function performed by the premotor cortex?

A

Concerned with movement planning and regulates externally cued movements

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10
Q

What area is responsible for planning internally cued movements?

A

Supplementary motor area

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11
Q

What structure is included in the midbrain?

A

Cerebral peduncles

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12
Q

Where do the majority of descending motor fibres decussate?

A

Medulla

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13
Q

What tract is formed from decussated upper motor neurone fibres?

A

Lateral corticospinal tract

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14
Q

What tract is formed from the ipsilateral upper motor neurone fibres?

A

Anterior corticospinal tract

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15
Q

Which muscles are innervated by the anterior corticospinal tract?

A

Trunk (axial) muscles

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16
Q

Which muscles are innervated by the lateral corticospinal tract?

A

Limb muscles

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17
Q

Who is the primary motor cortex arranged?

A

Somatopically

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18
Q

Which brainstem cranial nuclei are responsible for innervating the extra-ocular muscles?

A

Oculomotor, trochlear and abducens nerve

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19
Q

Where do the upper motor neurones synapse within the corticobulbar tract?

A

Synapse within the brainstem cranial nuclei

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20
Q

What structures are innervated by the facial nerve?

A

Muscles of the face

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21
Q

What structure is innervated by the hypoglossal nerve?

A

Tongue

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22
Q

What structures are innervated by the trigeminal nerve?

A

Muscles of mastication

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23
Q

Where are the lower motor neurones located within the extrapyramidal tracts?

A

Within the brainstem nuclei

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24
Q

Which extrapyramidal tract is responsible for stabilising the head during body movements, and coordinates with eye movements?

A

Vestibulospinal tract

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25
Q

What is the function of the vestibulospinal tract?

A

Stabilises head during body movements or as head moves. Coordinate head movements with eye movements and mediates postural adjustments.

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26
Q

What is the function of the reticulospinal tract?

A

Most primitive descending tract – from medulla and pons. Changes in muscles tone associated with voluntary movement and concerned with postural stability.

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27
Q

What is the function of the tectospinal tract?

A

From superior colliculus of midbrain. Orientation of head and neck during eye movements.

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28
Q

Where within the midbrain are the lower motor neurones arise from for the tectospinal tract?

A

Superior colliculus

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29
Q

Where do the lower motor neurones arise from for the rubrospinal tract?

A

Red nucleus of the midbrain

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30
Q

What is the function of the rubrospinal tract?

A

Innervates lower motor neurones of flexors of the upper limb. The corticospinal tract dominates rubrospinal activity.

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31
Q

What are the negative signs for a patient with an upper motor neurone lesion?

A

There is a loss of voluntary motor function
Paresis (graded weakness of movements)
Paralysis (plegia): Complete loss of voluntary muscle activity

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32
Q

What are the four main positive signs of an upper motor neurone lesion?

A

Spasticity: Increased muscle tone
Hyperreflexia: Exaggerated reflexes
Clonus: Abnormal oscillatory muscle contractions
Babinski’s sign

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33
Q

What is apraxia?

A

A disorder of skilled movement, patients are not paretic however lost information regarding how to perform skilled movements

34
Q

Which cerebral lobe lesions are commonly associated with apraxia?

A
Lesion of inferior parietal lobe.
Frontal lobe (premotor cortex and supplementary motor area)
35
Q

Which motor areas are affected in apraxia?

A

Supplementary motor area (SMA) and premotor cortex

36
Q

What are the most common causes of apraxia?

A

Strokes and dementia

37
Q

Why do positive signs occur in an upper motor lesion?

A

Increased abnormal motor function due to loss of inhibitory descending inputs

38
Q

Where do lower motor neurones reside?

A

Within cranial nuclei to corticobulbar tracts or within spinal cord for innervating limb muscles

39
Q

What are the 6 main signs of a lower motor neurone lesion?

A

1) Weakness
2) Muscle wasting (atrophy)
3) Tongue fasciculations and wasting
4) Hypotonia (reduces muscle tone)
5) Hyporeflexia (reduced reflexes)
6) Fibrillations

40
Q

What are fasciculations?

A

Damaged motor units produce spontaneous action potentials resulting in a visible twitch.

41
Q

What are fibrillations?

A

Spontaneous twitching of individual muscle fibres; recorded during electromyography examination

42
Q

What is another term used to describe motor neurone disease?

A

Amyotrophic lateral sclerosis

43
Q

What is motor neurone disease?

A

Progressive neurodegenerative disorder of the motor system (upper and lower motor neurones)

44
Q

What are the upper motor neurone signs in motor neurone disease?

A
  • Spasticity (Increased tone of limbs and tongue).
  • Brisk limbs and jaw reflexes
  • Babinski’s sign: Palmar extension of the toes upon stimulation is indicative of a corticospinal tract lesion, a typical response is concerned with palmar flexion.
  • Loss of dexterity
  • Dysarthria (Difficulty speaking)
  • Dysphagia (Difficulty swallowing).
45
Q

What is Babinski’s sign?

A

Palmar extension of the toes upon stimulation is indicative of a corticospinal tract lesion, a typical response is concerned with palmar flexion.

46
Q

Muscle atrophy is an example of what type of motor neurone lesion?

A

Lower motor neurone

47
Q

Fasciculations is an example of what type of motor neurone lesion?

A

Lower motor neurone

48
Q

Babinski’s sign is an example of what type of motor neurone lesion?

A

Upper motor neurone

49
Q

What are the 7 main structures of the basal ganglia?

A
Caudate nucleus 
Putamen 
External globus pallidus
thalamus
nucelus accumbens
amygdala 
anterior commisure
50
Q

The subthalamic nucleus is associated with which other basal ganglia structure?

A

Globus pallidus

51
Q

Which type of neurones are affected in Parkinson’s disease?

A

Dopaminergic neurones

52
Q

Which basal ganglia structure is predominantly affected in Parkinson’s disease?

A

Substania nigra

53
Q

The dopaminergic neurones originating in the substantia nigra project to which structure?

A

Striatum

54
Q

What are the 5 main clinical presentations of Parkinson’s disease?

A
Bradykinesia
Hypomimic face
Akinesia
Rigidity (muscle tone increases, causing resistance to externally imposed joint movements) 
Tremor at rest
55
Q

What is bradykinesia?

A

Slowness of small movements

56
Q

What is a hypomimic face?

A

Expressionless (absence of movements that normally animate the face).

57
Q

What is akinesia?

A

Difficulty in the initiation of movements because cannot initiate movements internally

58
Q

What type of neurones are affected in Huntington’s disease?

A

GABAergic neurones

59
Q

Which basal ganglia structures are affected in patients with Huntington’s disease?

A

Striatum
Caudate
Putamen

60
Q

What is the inheritance pattern of Huntington’s disease?

A

Autosomal dominant

61
Q

What type of mutation is inherited in a patient with Huntington’s disease?

A

CAG repeat

62
Q

What are the presenting symptoms in a patient with Huntington’s disease?

A

Choreic movements (chorea)- rapid jerky involuntary movements of the body hands and face a

Speech impairment
Difficulty swallowing (dysphagia)
Unsteady gait
Later stages, cognitive decline and dementia

63
Q

Which part of the body is affected first by choreic movements?

A

Hands and face affected first, then legs

64
Q

Which basal ganglia structure is associated with Ballism?

A

Subthalamic nucleus

65
Q

What is ballism?

A

Sudden uncontrolled flinging of the extremities, symptoms occur contralaterally

66
Q

Where is the cerebellum located?

A

Posterior cranial fossa

67
Q

Which structure separates the cerebrum from the cerebellum?

A

Tentorium cerebelli

68
Q

What is the main function of the cerebellum?

A

Coordinator and predictor of movement

69
Q

Which cerebellum structure is associated the regulation of gait, posture and equilibrium?

A

Vestibulocerebellum

70
Q

A tumour to the vestibulocerebellum can cause what type of symptoms?

A

Symptoms of vestibular disease leading to gait ataxia and tendency to fall

71
Q

What is the function of the spinocerebellum?

A

Coordination of speech
Adjustment of muscle tone
Coordination of limb movements

72
Q

A lesion to the spinocerebellum can lead to what?

A

Causes abnormal gait and stance (wide-based)

Affects mainly legs

73
Q

Chronic alcoholism affects which part of the cerebellum?

A

Spinocerebellum

74
Q

Which cerebellar region is the most lateral?

A

Cerebrocerebellum

75
Q

What is the function of the cerebrocerebellum?

A

Coordination of skilled movements
Cognitive function, attention,
processing of language
Emotional control

76
Q

A lesion to the cerebrocerebellum affects what?

A

Mainly affects arms/skilled coordinated movements (tremor) and speech.

77
Q

What are the main signs of cerebellar dysfunction?

A
Ataxia
Dysmetria 
Intention tremor 
Dysdiadochokinesia 
Scanning speech
78
Q

What is dysmetria?

A

Inappropriate force and distance for target directed movements

79
Q

What is intention tremor?

A

Increasingly oscillatory trajectory of a limb in a target-directed movement

80
Q

What is dysdiadochokinesia?

A

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