Subcortical Motor Systems: Cerebellum & Basal Ganglia Lecture 21.
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Transcript of Subcortical Motor Systems: Cerebellum & Basal Ganglia Lecture 21.
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Subcortical Motor Systems:
Cerebellum & Basal Ganglia
Lecture 21
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Motor Loops
Cortex Subcortex Cortex Spinal cord
Cerebellum coordination of movement
Basal Ganglia selection & initiation of voluntary
movements ~
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Cerebellum
Nonmotor functions - memory/language Coordination of complex movements Programs ballistic movements
no feedback during execution direction, force, & timing
Motor learning shift from conscious unconscious ~
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Cerebellum: Anatomy
Folia & lobules analogous to sulci & gyri
Vermis - along midline output ventromedial pathway
Hemispheres output lateral pathway
Deep cerebellar nuclei analogous to thalamus ~
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Motor Loop Through Cerebellum
Lateral cerebellumsimplest circuit
20 million axons Cortex pons & cerebellum
Prefrontal, Motor, PPC Pons & Cerebellum thalamus
VLc - ventrolateral nucleus VLc M1 lateral pathway ~
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Prefrontal PPCM1M2
Pons, CerebellumVLc
Distal Limbs
Lateral CerebellarMotor Loop
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Cerebellum: Damage
Lesions - loss of motor coordination Dysynergia
no simultaneous movement of jointsserial movement only
Dysmetric movements to wrong coordinates
Alcohol intoxiction depression of cerebellar circuits ~
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Basal Ganglia
Caudate nucleus Putamen
Globus Pallidus Substantia Nigra Tegmentum
Control slow movements Using immediate sensory feedback ~
Striatum
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StriatumGlobusPallidus
Substantia Nigra
Thalamus
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Cross section of Tegmentum
Substantia Nigra
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Prefrontal PPCM1M2
BasalGanglia VLo
Distal Limbs
Basal GangliaMotor Loop
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Basal Ganglia Movement Disorders
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Parkinson’s Disease
1% of population Nigrostriatal pathway
Substantia nigra neurons die Progressive loss
Hypokinesia Rigidity Bradykinesia Akinesia ~
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SMA
Putamen
-Globus
Pallidus (GPi)
-
SubstantiaNigra
+
VLo
SubthalamicNucleus
+
Cortex
+X
Parkinson’s Disease+
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Parkinson’s Disease: Treatment
Basal Ganglia - Cholinergic Substantia Nigra - Dopaminergic Drug Therapy
L-DOPA Pallidectomy Tissue transplants ~
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Huntington’s Disease (Chorea)
Rare onset 30-40s
early as 20s Degeneration of Striatum
Caudate Putamen
GABA & ACh neurons ~
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Symptoms
Khoros = dance Uncontrollable, jerky movements Dementia Progressive
eventually fatal ~
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SMA
Putamen
-
-
+
VLo
SubthalamicNucleus
+X
Huntington’s Disease
GPiGPe
-
+
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Huntington’s Disease: Cause
Genetic disorder Single dominant gene on chromosome 4 HD mutation -
unstable trinucleotide repeat - CAG # of repeats correlated w/ age of onset ~
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HD gene huntingtin 3 forms
mutated form binds to protein involved in energy production neuron starves
Excitotoxicity contributes to degeneration glutamate Nitric oxide (NO) Potential treatment:: Inhibit NO synthase ~
Huntington’s Disease: Cause
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Hyperkinesia
Excessive movement Ballism
violent, flinging movements Lesions in subthalamus
less inhibition of VLo excitation of SMA ~
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SMA
Striatum
- GlobusPallidus
-
+
VLo
SubthalamicNucleus
+
X
Hyperkinesia(e.g. ballism)