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What are the "true" basal ganglia?
- Caudate
- Putamen
- Globus Pallidus
- Amygdala
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Corpus Striatum
- Caudate
- Putamen
- Globus Pallidus
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What are the major functions of the basal ganglia?
- Regulate somatic motor activity via thalamusSequence together basic movements
- Motor learning/planning
- Eye movement control
- Emotions/motivations
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Which basal ganglia are the input nuclei and what is their function?
- The striatum (caudate and putamen)
- Recieve inputs from cerebral cortex
- Project to other basal ganglia
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Which basal ganglia are the output nuclei and what is their function?
- Medial Pallidal Segment, Substantia Nigra (Pars Reticulata)
- Recieve input from striatum and intrinsic nuclei
- Project to thalamus (VA and VLa)
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What are the intrinsic nuclei and why are they different?
- Lateral Pallidal Segment (LPS)
- Subthalamic Nucleus (STN)
- communicate only with other basal ganglia nuclei
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What is the Direct Pathway and what is its function?
- Striatum --> MPS/SNr
- Facilitates movement via excitatory effect
- Bypasses intrinsic nuclei
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What is the Indirect Pathway and what is its function?
- Striatum --> intrinsic nuclei --> MPS/SNr
- Suppresses movement via inhibitory effect
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What are the functions of spiny striatal neurons?
What is anatomically distiguishable about them?
- Recieve inputs to the striatum
- Provide output from the striatum
- Have dendritic spines
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What is the function of aspiny striatal neurons?
What is anatomically distinguishable about them?
- Modulate spiny striatal activity
- Lack dendritic spines
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What is the neurotransmitter combination specific to the Direct Pathway?
GABA/Substance P
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What is the neurotransmitter combination specific to the Indirect Pathway?
GABA/Enkephalin
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What is the effect of dopamine in the basal ganglia?
- Facilitates activation of the Direct Pathway
- Suppresses activation of the Indirect Pathway
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What are corticostriate fibers?
Where are they?
- Cortical inputs to the basal ganglia
- Internal and external capsules
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What are pallidothalamic fibers?
Connections from the MPS to the thalamus
- Ansa lenticularis - from lateral MPS
- Lenticular Fasciculus - from medial MPS
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What is the Prerubral Field?
Convergence of the lenticular fasciculus and ansa lenticularis ventral to the thalamus
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What is the Subthalamic Fasciculus?
Connections between the Globus Pallidus and the Subthalamic Nucleus
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Examples of hypokinetic movement disorders
- Bradykinesia
- Hypokinesia
- Akinesia
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Bradykinesia
Movements are slow and difficult to initiate
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1. Hypokinesia
2. Akinesia
1. Decreased movement
2. Absence of movement
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Dyskinesia - definition and examples
Abnormal involuntary movements
- Resting Tremor
- Dystonia
- Athetosis
- Chorea
- Ballismus
- Tics
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Resting Tremor
- Rhythic, oscillating movements
- Often goes away during voluntary movements
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Dystonia
Sustained contractions
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Athetosis
Slow, twisting or writhing movements
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Chorea
Continuous, non-purposeful movements (jerky or fluid)
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Ballismus
Large, flinging movements of proximal limb muscles
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Tics
Fast, repetitive movement - patient feels urge to do so
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1. Rigitiy
2. Hypotonia
1. Increased resistence to passive movement - often in hypokinetic disorders
2. Decrease tone, resistance - sometime in hyperkinetic disorders
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1. A lesion that favors the direct pathway...
2. A lesion that favors the indirect pathway...
- 1. Hyperkinetic disorder
- 2. Hypokinetic disorder
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Parkinson's disease
1. Cause
2. Result
3. Treatments
- 1. Loss of dopaminergic neurons in SNpc
- 2. Hypokinetic symptoms
- 3. Dopamine precursors, agonists
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Huntington's disease
1. Cause
2. Result
3. Treatments
- 1. Progressive atrophy of striatum (especially GABA/enkephalin spiny neurons)
- 2. Hyperkinetic symptoms (chorea), dementia
- 3. Tetrabenzine and dopamine antagonists
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Ballism/Hemiballism
1. Cause
2. Result
3. Treatments
- 1. Usually vascular lesion of subthalamic nucleus
- 2. Hyperkinetic signs (reduced indirect pathway) - ballismus
- 3. Anti-dopaminergics
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