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Clinical neuroscience > Disorders of the motor system > Flashcards

Disorders of the motor system Flashcards

Review Parkinson's flow diagram

1
Q

Outline the anatomy of the basal ganglia

A
  • Substantia nigra pars compacta
  • Striatum (consists of caudate nucleus and putamen)
  • Globus pallidus (internal and external segment)
  • Lentiform nucleus (consists of putamen and globus pallidus)
  • Subthalamic nucleus
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2
Q

How does the basal ganglia communicate with the motor cortex?

A
  • Via the thalamus
  • Increased thalamic activity causes increased cortical activity and vice versa
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3
Q

What is the normal function of the basal ganglia

A
  • Unclear
  • Probable role in reinforcing appropriate movements and removing inappropriate movements
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4
Q

What reinforces appropriate movements?

A
  • Direct pathways
  • Excitatory to motor cortex
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5
Q

What edits out appropriate movements?

A
  • Indirect pathways
  • Inhibitory to motor cortex
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6
Q

What role does dopamine play in movement?

A
  • Facilitates movement by exciting the motor cortex
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7
Q

How does dopamine excite the motor cortex?

A
  • Stimulates excitatory D1 receptors on striatal neurones of direct pathway
  • Inhibits indirect pathway by activating D2 receptors on striatal neurones
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8
Q

Which motor cortex is regulated by the basal ganglia?

A
  • Basal ganglia regulate ipsilateral motor cortex
  • So if SNc is affected unilaterally there are contralateral signs
  • Due to decussation of the corticospinal tract
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9
Q

Outline the indirect pathway of the basal ganglia

A
  • Subthalamic nucleus is inhibited
  • This then allows glutamate to excite the globus pallidus internal segment
  • Because globus pallidus internus is excited, it is able to inhibit the thalamus
  • This allows inhibition of movement
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10
Q

Outline the direct pathway of the basal ganglia

A
  • Putamen sends inhibitory signals to Globus Pallidus internal segment
  • Because Globus Pallidus is inhibited, it can no longer inhibit the thalamus
  • So the thalamus is able to excite the cortex and cause movement
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11
Q

What is the inhibitory neurotransmitter in the basal ganglia?

A
  • GABA
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12
Q

What causes Parkinson’s disease?

A
  • Degeneration of dopaminergic neurones in SNc (substantia nigra pars compacta)
  • So patients lose the dopamine-driven facilitation of movement via both pathways
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13
Q

What are the symptoms and signs of Parkinson’s disease?

A
  • Tremor
  • Rigidity
  • Bradykinesia
  • Hypophonia (quiet speech)
  • Decreased facial movement
  • Micrographia
  • Dementia
  • Depression
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14
Q

Why does Parkinson’s cause tremor?

A
  • Unclear mechanism
  • May be related to dysfunction of indirect pathway which would normally suppress unwanted movements
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15
Q

Why does Parkinson’s cause rigidity?

A
  • Unknown mechanism
  • May be related to lack of coordination between agonists and antagonists
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16
Q

Why does Parkinson’s cause bradykinesia?

A
  • Best understood mechanism
  • Slow movements due to loss of cortical excitation
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17
Q

Why does Parkinson’s cause hypophonia?

A
  • Bradykinesia of larynx and tongue
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18
Q

Why does Parkinson’s cause decreased facial movement?

A
  • Bradykinesia of face
19
Q

Why does Parkinson’s cause micrographia?

A
  • Bradykinesia of hands
20
Q

Why does Parkinson’s cause dementia?

A
  • Possible progression of currently unknown causative agents e.g. protein aggregates
21
Q

Why does Parkinson’s cause depression?

A
  • Basal ganglia also have a role in cognition and mood
22
Q

What is Huntington’s chorea?

A
  • Autosomal dominant progressive disorder
  • Early onset of around 30-50 years old
23
Q

What are the early stages of Huntington’s chorea associated with?

A
  • Loss of inhibitory projections from striatum to the external segment of the globus pallidus
  • This leads to hyperkinetic features (brakes have been taken off the thalamus)
24
Q

What are the features of Huntington’s chorea?

A
  • Chorea (dance-like movements)
  • Dystonia
  • Loss of co-ordination
  • Cognitive decline and behavioural disturbances
25
Q

Why does Huntington’s chorea lead to chorea?

A
  • Increased motor cortex activation
26
Q

Why does Huntington’s chorea lead to dystonia?

A
  • Uncomfortable contractions of agonists and antagonists simultaneously
  • Leads to odd postures caused by over activity in agonist/antagonist muscle circuits and loss of co-ordination between these
27
Q

What is Hemiballismus?

A
  • Rare disorder
  • Can be caused by damage to subthalamic nucleus which normally inhibits the thalamus via GPi
28
Q

What causes hemiballismus?

A
  • Subcortical stroke (lacunar infarct)
29
Q

What does hemiballismus cause?

A
  • Unilateral explosive (ballistic) movements
30
Q

Outline the anatomy of the cerebellum

A
  • Midline vermis and two laterally placed hemispheres
  • Communicates with the rest of the CNS via the cerebellar peduncles
  • Sits above fourth ventricle
31
Q

What does the cerebellum deal with?

A
  • Trunk,
  • Hemispheres deal with ipsilateral side of the body
32
Q

What do the different peduncles connect to?

A
  • Superior cerebellar peduncle connects to midbrain
  • Middle cerebellar peduncle connects to pons
  • Inferior cerebellar peduncle connects to medulla
33
Q

Why is the anatomical position of the cerebellum clinically important?

A
  • Cerebellar lesions (e.g. tumours) can cause hydrocephalus
34
Q

What are the normal functions of the cerebellum?

A
  • Obscure
  • Has a clear role in the sequencing and coordination of movements
  • Uses sensory information to decide upon the most appropriate sequence of movements to perform an action
35
Q

How does the cerebellum work with the basal ganglia?

A
  • Basal ganglia decides what the most appropriate movements are
  • Cerebellum then sequences movement
36
Q

Where does the cerebellum receive sensory input from?

A
  • Has profuse sensory inputs from proprioceptive neurones and sensory cortices
  • Receives sensory input from ipsilateral spinal cord and contralateral sensory cortices
37
Q

Where does the cerebellum send its outputs to?

A
  • Contralateral motor cortex
  • Signs of cerebellar damage are ipsilateral due to decussation of corticospinal pathway
38
Q

What are some signs of cerebellar dysfunction?

A
  • Dysdiadochokinesia
  • Ataxia
  • Nystagmus
  • Intention tremor
  • Slurred speech
  • Hypotonia
39
Q

What is dysdiadochokinesia?

A
  • Difficulty with rapidly alternating movements
40
Q

What is ataxia?

A
  • Unsteady gait as a result of difficulty sequencing lower limb muscle contractions as well as loss of unconscious proprioception from lower limbs
41
Q

What is nystagmus?

A
  • Flickering eye movements due to malcoordination of extraocular muscles
42
Q

What is an intention tremor?

A
  • A tremor that worsens as a target is approached
43
Q

What causes dysarthria?

A
  • Malcoordination of laryngeal and tongue musculature

Clinical neuroscience (19 decks)

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