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NHB > Basal Ganglia > Flashcards

Basal Ganglia Flashcards

1
Q

What are the basal ganglia?

A

Collection of large subcortical forebrain nuclei

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2
Q

What are the main nuclei of the basal ganglia?

A
  1. Caudate
  2. Putamen
  3. Globus pallidus (internal and external)
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3
Q

What are these nuclei also referred as?

A

Corpus striatum

Grey matter crossed by white fibres from motor cortex giving striped appearance

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4
Q

What are the midbrain nuclei that are functionally connected to the basal ganglia?

A
  1. Substantia nigra

2. Subthalamic nucleus

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5
Q

Where do the major inputs to the basal ganglia come from?

A

Cerebral cortex (all lobes)

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6
Q

What are the outputs of the basal ganglia?

A

Inhibitory

Directed to parts of the thalamus that supply almost all parts of the frontal lobes

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7
Q

What connects the nuclei of the basal ganglia?

A

Sequential GABA inhibitory connections

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8
Q

What are the symptoms of basal ganglia dysfunction?

A

Problems with either excess (hyperkinesia) or paucity (hypokinesia) of movement

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9
Q

What is hyperkinesia?

A

Excessive movement

  1. Chorea
  2. Athetosis
  3. Ballismus
  4. Dyskinesia
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10
Q

What is chorea?

A

Unexpected ‘dancing’ movement

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11
Q

What is athetosis?

A

Writhing movement of hands or face

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12
Q

What is ballismus?

A

Flailing ballistic movements

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13
Q

What is dyskinesia?

A

Unpredictable movements

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14
Q

What is hypokinesia?

A

Reduction in movement

  1. Bradykinesia
  2. Rigidity
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15
Q

What is bradykinesia?

A

Slowness

Parkinsonism

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16
Q

What is the extrapyramidal motor system?

A

Basal ganglia disorder

Misleading term as still involves pyramidal motor system (corticospinal tract)

Abnormal pattern of activity through normal pyramidal tract

17
Q

What is the direct pathway in the basal ganglia?

A
  1. Corticostriate fibres activate neurons in caudate/putamen
  2. These neurons inhibit neurons in globus pallidus internus
  3. These neurons tonically inhibit neurons in the thalamus

Thus activation of this pathway leads to disinhibition of thalamus, permitting movement

18
Q

What is the indirect pathway in the basal ganglia?

A
  1. Corticostriate fibres activate different neurons in caudate/putamen
  2. These neurons inhibit neurons in globus pallidus externus
  3. These neurons inhibit neurons in the subthalamic nucleus
  4. These neurons excite neurons in the globus pallidus internus

Thus activation of this pathway increases inhibition, preventing movement

19
Q

What causes Parkinson’s disease?

A

Degeneration of substantia nigra leads to loss of dopamine causing imbalance in basal ganglia pathways

Causes reduced activity in direct pathway and increased activity in indirect pathway

20
Q

What do D1 receptors do?

A

Dopamine receptor

Facilitates pathway to globus pallidus internus

21
Q

What do D2 receptors do?

A

Dopamine receptor

Suppresses pathway to globus pallidus externus

22
Q

How is Parkinson’s disease treated surgically?

A
  1. Controlled lesions of globus pallidus (pallidotomy) to reduce inhibition of thalamus
  2. Deep brain stimulation of subthalamic nucleus to reduce activity in subthalamic nucleus
23
Q

What is the role of the dorsal striatum?

A

Motor function

  1. Motor circuit with input from sensorimotor cortex and output to primary motor cortex and SMA
  2. Oculomotor circuit with input from visual association cortex and output to frontal eye fields
24
Q

What is the role of the ventral striatum?

A

Higher level function such as deciding between options and motivation for action

  1. Prefrontal cortex association circuit with input from association cortex and output to prefrontal cortex (executive function)
  2. Limbic circuit with anterior cingulate gyrus and orbitofrontal cortex
25
Q

What is the physiological role of the basal ganglia?

A

Decision making

Action selection

26
Q

How does the basal ganglia control saccadic movement?

A
  1. Tonic inhibition of superior colliculi by substantia nigra
  2. Cerebral cortex can activate appropriate cells in caudate/putamen to disinhibit superior colliculi
  3. Saccade allowed to occur

Basal ganglia decide whether and when a saccade occurs

27
Q

What is the physiological role of dopamine?

A

Mediates plasticity of the corticostriate inputs to the caudate and putamen

Release of dopamine reinforces inputs that were active to generate successful output

Important in habit learning

Reward processes

NHB (17 decks)

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