FNS 30 Basal Ganglia and Related Structures
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What are the "true" basal ganglia?
- Globus Pallidus
- Globus Pallidus
What are the major functions of the basal ganglia?
- Regulate somatic motor activity via thalamusSequence together basic movements
- Motor learning/planning
- Eye movement control
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
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)
What are the intrinsic nuclei and why are they different?
- Lateral Pallidal Segment (LPS)
- Subthalamic Nucleus (STN)
- communicate only with other basal ganglia nuclei
What is the Direct Pathway and what is its function?
- Striatum --> MPS/SNr
- Facilitates movement via excitatory effect
- Bypasses intrinsic nuclei
What is the Indirect Pathway and what is its function?
- Striatum --> intrinsic nuclei --> MPS/SNr
- Suppresses movement via inhibitory effect
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
What is the function of aspiny striatal neurons?
What is anatomically distinguishable about them?
- Modulate spiny striatal activity
- Lack dendritic spines
What is the neurotransmitter combination specific to the Direct Pathway?
What is the neurotransmitter combination specific to the Indirect Pathway?
What is the effect of dopamine in the basal ganglia?
- Facilitates activation of the Direct Pathway
- Suppresses activation of the Indirect Pathway
What are corticostriate fibers?
Where are they?
- Cortical inputs to the basal ganglia
- Internal and external capsules
What are pallidothalamic fibers?
Connections from the MPS to the thalamus
- Ansa lenticularis - from lateral MPS
- Lenticular Fasciculus - from medial MPS
What is the Prerubral Field?
Convergence of the lenticular fasciculus and ansa lenticularis ventral to the thalamus
What is the Subthalamic Fasciculus?
Connections between the Globus Pallidus and the Subthalamic Nucleus
Examples of hypokinetic movement disorders
Movements are slow and difficult to initiate
1. Decreased movement
2. Absence of movement
Dyskinesia - definition and examples
Abnormal involuntary movements
- Resting Tremor
- Rhythic, oscillating movements
- Often goes away during voluntary movements
Slow, twisting or writhing movements
Continuous, non-purposeful movements (jerky or fluid)
Large, flinging movements of proximal limb muscles
Fast, repetitive movement - patient feels urge to do so
1. Increased resistence to passive movement - often in hypokinetic disorders
2. Decrease tone, resistance - sometime in hyperkinetic disorders
1. A lesion that favors the direct pathway...
2. A lesion that favors the indirect pathway...
- 1. Hyperkinetic disorder
- 2. Hypokinetic disorder
- 1. Loss of dopaminergic neurons in SNpc
- 2. Hypokinetic symptoms
- 3. Dopamine precursors, agonists
- 1. Progressive atrophy of striatum (especially GABA/enkephalin spiny neurons)
- 2. Hyperkinetic symptoms (chorea), dementia
- 3. Tetrabenzine and dopamine antagonists
- 1. Usually vascular lesion of subthalamic nucleus
- 2. Hyperkinetic signs (reduced indirect pathway) - ballismus
- 3. Anti-dopaminergics
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