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Control & Movement > Control L19 Basal Nuclei > Flashcards

Control L19 Basal Nuclei Flashcards

1
Q

What is another name for basal nuclei?

A

Basal ganglia

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2
Q

What is the function of the basal nuclei?

A

To modulate movement by providing a feedback mechanism to the cerebral cortex for normal initiation, control and cessation of motor response.
Cognitive processes
Emotional behaviour

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3
Q

Is the basal ganglia grey or white matter?

A

Masses of grey matter

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4
Q

What is dyskinesias?

A

Abnormal involuntary movement

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5
Q

What symptom is characteristic of a lesion at the basal ganglia?

A

Dyskinesia

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6
Q

What are the 5 components of the basal ganglia?

A

Caudate nucleus
Putamen
Globus pallidus
Substantia nigra
Subthalamic nucleus

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7
Q

What is the difference between nuclei and ganglia?

A

Nuclei = group of cell bodies in CNS
Ganglia = group of cell bodies in PNS

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8
Q

What part of the brain is the substantia nigra found?

A

Mesencephalon

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9
Q

What part of the brain is the subthalamic nucleus found?

A

Diencephalon

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10
Q

What part of the brain are the caudate nucleus, putamen and globus pallidus found?

A

Telencephalon

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11
Q

What are the caudate nucleus and putamen collectively known as?

A

(Neo)striatum

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12
Q

What is another name for the globus pallidus?

A

Paleostriatum

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13
Q

What is the collective name for the caudate nucleus, putamen and globus pallidus?

A

Corpus striatum

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14
Q

What is formed by the putamen and globus pallidus?

A

Lentiform nucleus

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15
Q

What are the two areas of the globus pallidus?

A

Internus (more medial)
Externus (more lateral)

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16
Q

What are the two parts of the substantia nigra?

A

Pars reticulata
Pars compacta

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17
Q

What part of the globus pallidus works with which part of the substantia nigra to perform the same function?

A

Internus and para reticulata

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18
Q

Where is the subthalamic nucleus found in relation to the thalamus?

A
19
Q

What white matter structure are closely associated with the internal capsule?

A

Optic radiations

20
Q

Where do you need to make a section to appreciate the subthalamic nucleus?

A

Coronal section of posterior third of diencephalon

21
Q

Where is substantia nigra found?

A

In the midbrain seen on the posterior aspect of thalamus in a coronal plane of posterior 1/3 of diencephalon

22
Q

Where is the substantia nigra reticularis in relation to compacta?

A

More anterior to substantia nigra compacta

23
Q

What chemical is highly concentrated in the substantia nigra compacta?

A

Dopamine

24
Q

What arteries supply the deep basal ganglia structures and internal capsule?

A

Lenticulostriate arteries

25
Q

What artery does the lenticulostriate arteries arise from?

A

MCA

26
Q

How does the basal ganglia send signals?

A

Via multiple parallel looping circuits in order to modulate cortical output

27
Q

What prevents the thalamus from continuously exciting the cerebral cortex?

A

Due to inhibition of the thalamus by the Globus pallidus and substantia nigra reticulata

28
Q

How is dopamine involved in circuitry of the basal ganglia?

A

Dopamine release by the substantia nigra compacta acts on the input nuclei of the neostriatum which sends signals via the direct or indirect pathway to the output nuclei.

29
Q

What is the direct pathway of the basal nuclei?

A

The pathway which inhibits the inhibitory neurons (disinhibition) affecting the thalamus, allowing the thalamus to excite the cerebral cortex to initiate voluntary movement.

30
Q

What is the indirect pathway of the basal nuclei?

A

The pathway which excites the inhibitory neurones (enhanced inhibition) of the thalamus, which prevent activation of the cerebral cortex preventing involuntary movement.

31
Q

How does the direct pathway work?

A

The neuron from the cortex to the input nuclei of neostriatum excites the inhibitory neuron between the neostriatum and the globus pallidus internus.
This inhibits the inhibitory neuron between the globus pallidus internus and the thalamus.
This causes disinhibition at the thalamus allowing the excitary neuron between the thalamus and cortex to be activated resulting in movement.

32
Q

How does dopamine production affect the direct pathway?

A

When dopamine produced by the substantia nigra comes into contact with D1 receptors of the direct pathway, there is enhanced inhibitor of the neuron between the neostriatum and globus pallidus internus resulting in increased activation at the thalamus resulting in increased movement.

33
Q

How does the indirect pathway work to inhibit movement?

A

Excitary neurones from the cortex to the neostriatum cause activation of the inhibitory neuron between the neostriatum and globus pallidus externus.
The activation of this inhibitory neuron causes disinhibition of the the following inhibitory neuron between the globus pallidus externus and the subthalamic nucleus.
This means the excitary neuron between the subthalamic nucleus and globus pallidus internus is activated leading to activation of the inhibitory neuron between the globus pallidus internus and the thalamus.
This inhibitory neuron inhibits the thalamus from exciting the cortex preventing involuntary movement.

34
Q

How does the release of dopamine affect the inhibitory pathway?

A

Dopamine binds to D2 receptors and has inhibitory effects on the fibres which project from the striatum to the globus pallidus externus

35
Q

What are the two different effects of a lesion in the basal ganglia?

A
  1. Lesion increases output from basal nuclei causing movement.to be slowed = hypokinetic
  2. Lesion decreases output from the basal nuclei causing increase in abnormal and involuntary movements during rest = hyperkinetic
36
Q

What is the most common disease of the basal ganglia?

A

Parkinson’s disease

37
Q

What is Parkinson’s disease?

A

A disease where there is a dopaminergic deficit in the brain

38
Q

What are symptoms of Parkinson’s disease?

A

Bradykinesia/hypokinesia - decreases or slowness of movement with poor initiation which can present as walking slowly with little steps - a shuffling/Parkinson’s gate
Resting tremor
Rigidity
Expressionless face

39
Q

What areas of the brain have been degraded in patients with Parkinson’s disease?

A

Dopamine producing areas e.g. substantia nigra

40
Q

What is characteristic of the basal ganglia in Parkinson’s disease?

A

Presence of lewy bodies

41
Q

What are examples of hyperkinetic diseases?

A

Chorea aka Huntington’s disease
Hemiballismus

42
Q

What is Chorea?

A

Aka as Huntington’s disease, it is degeneration of inhibitory fibres from the striatum to the globus pallidus externus. It is an inherited dominant illness caused by a defect in the protein huntingtin

43
Q

What is hemiballismus?

A

Degeneration/lesion of the subthalamic nucleus

Control & Movement (36 decks)

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