Neural Control of Muscle

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Neural Control of Muscle
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Quick Review Spinal Cord
Flexors
Extensors
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Quick Review Spinal Reflex Pathways
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Quick Review Spinal Reflex Pathways
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Basal Ganglia
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Basal Ganglia Circuitry Motor Regions project
mainly to Putamen
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Motor Topography is preserved in Basal Ganglia
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Caudate Putamen Pallidum (thalamus, hippo.)
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Ventral Striatum (Nucleus Accumbens)
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Subthalamic Nucleus Substantia Nigra
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Basal Ganglia as a Gating Mechanism
Tonic output from basal ganglia on cortex is
inhibitory
Globus Pallidus
Inhibition
Thalamus/Cortex
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Basal ganglia and response initiation
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Consequences of Selective BG Activation
Striatum
Striatum
Globus Pallidus
Globus Pallidus
Thalamus/Cortex
Thalamus/Cortex
Increased Inhibition
Disinhibition (Gating)
Excitation
Inhibition
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Parkinsons Disease involves increased tonic
inhibition. A stuck gate.
Normal Parkinsons
Globus Pallidus
Globus Pallidus
Thalamus/Cortex
Thalamus/Cortex
Inhibition
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Akinesia Due to Elevated Threshold
Input pattern is unchanged. But stronger
activation is required to trigger the action.
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Disorders of the Motor System Structure
Defecit Motor Cortex Lose Power and
Precision Secondary Motor Areas Apraxia (loss of
precision) Cerebellum Ataxia (difficulty
walking) Basal Ganglia Parkinsons
Disease Huntingtons Disease Hemiballism

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L-dopa therapy Restores Motor Function in
Parkinsons Disease One of the miracles of 20th
Century Medicine. But problems can develop over
time, and some patients dont respond well to
L-dopa drugs.
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Deep Brain Stimulation (DBS)
Black Presurgery White With stimulation
Subthalamic nucleus Globus pallidus, Internal
Segment
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Basal Ganglia are not entirely a motor structure

• Birdsong is largely stored in the basal ganglia
  (speech, perhaps?)
• Parkinson Patients have cognitive deficits as well

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• Basal ganglia system essential for shifting from
  one goal state to another.
• Motor domain Akinesia
• Parkinson patients become stuck on current
  action unable to implement a new action.
• Cognitive domain Bradyphrenia (slowed thought)
• Parkinson patients have trouble switching from
  one mental set to another.