Principles of Neuroscience Lecture 14 Modulation of Movement Flashcards Preview

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Flashcards in Principles of Neuroscience Lecture 14 Modulation of Movement Deck (24)

Which two regions in the brain are modulatory centres for movement?

Basal Ganglia


Describe the structure of the basal ganglia

5 discrete regions:
Globus Pallidus
Sub-thalamic nuclei
Substantial nigra


Describe the localisation of the basal ganglia

Caudate: runs along edge of lateral ventricles
Putamen: base of forebrain - telencephalon
Globus pallidus: next to putamen : external then internal
Sub thalamic nuclei: under thalamus
Substantial nigra: mesencephalon - midbrain


What are the functions of the basal ganglia (3)

1. Initiation of movement
2. Optimisation of movement, evaluation
3. Selection of movements from a repertoire


What are the inputs to the Caudate-Putamen?

1. Cerebral cortex
2. Substantial nigra pars compacta


What are the two output pathways from the Caudate Putamen?



Describe the direct pathway

1. Caudate putamen actively inhibits Globus pallidus internal
2. GPi can no longer carry out its normal activity of inhibiting the thalamus
3. Thalamus is not inhibited, so it activates the motor cortex


Describe the indirect pathway

1. C-P inhibits the Globus Pallidus external
2. GPe can no longer inhibit the sub - thalamic nuclei, because it has been inhibited
3. Sub thalamic nucleus is not inhibited, so it excites the GPi
4. The GPi is activated, so it can carry out it's function of inhibiting the thalamus
5. The thalamus is inhibited, so it can't activate the motor cortex


What is the role of the direct pathway?

Selection and activation of the desired movements


What is the role of the indirect pathway?

Inhibition of competing movements


What are basal ganglia loops?

Such as those we see here. They talk to the cortex.
They aren't just associated with motor function


What are the two dopamine receptors in the Caudate-Putamen?
Where is the dopamine coming from?

D1: activates direct pathway
D2: inhibits the indirect pathway

Dopamine is coming from the substantial nigra pars compacta


Describe the pathology of Parkinson's disease?

The cells in the substantial nigra pars compacta die

Dopamine is no longer released onto the caudate-putamen

There is no longer activation of movement via the two pathways


When is a tremor first seen in Parkinson's?

When 80% of the cells in the substantial nigra are already dead


How does the substantial nigra pars compacta activate movement? (Two ways)

1. Activate the direct pathway, which is activating movement
2. Inhibits the indirect pathway, which is itself inhibitory. Thus, movement is activated


What is a treatment for Parkinson's?

Saturate brain in dopamine
Only regions that need it respond to it
C-P now has dopamine, and movement is activated

Deep brain stimulation:
Electrical stimulation of the C-P and GP
This causes retrograde activation of the pathway
This stops the tremor


Describe the pathology of Huntington's disease

Cells in C-P and GP die
GP normally inhibits the thalamus
No inhibition mean there are spontaneous and jerky movements


What is the striatum?

This is the caudate and the putamen


Describe deep brain stimulation?

Stimulation of the sub thalamic nucleus
Retrograde activation of the pathway, stopping the tremor and activating movement


Describe the functions of the Cerebellum (3)

1. Start and stopping of movements: coordination
2. Motor learning
3. Plan formation
4. Maintenance of muscle tone

Does not itself initiate movement


Where is the cerebellum?

Hindbrain: metencephalon


What are the inputs to the cerebellum?

Frontal cortex
Vestibular nuclei


What are the outputs from the cerebellum?

Motor cortex


What is ataxia?
Describe the symptoms seen in a clinical test

Ataxia: "can't follow the path". This is when movement is inefficient because the brain does not form a plan about where the limb should go.
Eg. Touch a spot, then touch you nose
The path is not direct
The patient does not have the feed forward information

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