Transcript Central Pattern Generators

Change of location for class
as of Monday Jan. 23
Odette Building room 112
Friday Jan. 20, 2006
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Central Pattern Generators
• Local circuits in the spinal
cord
• Can control complex timing
and coordination of complex
movement patterns.
• In cats, timing of movements
is accomplished at the spinal
cord level, but not support.
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Central Pattern Generators
• Each limb has its own cpg
• Cpg’s are connected by local circuits
• Cpg’s in humans, may have more
regulatory input from upper motor
neuron pathways.
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Lamprey cpg’s
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Spinal cord innervates muscle segments
Identified mns in stereotyped positions
Intrinsic firing pattern
Know know nt’s, firing patterns, regulation of
all components
• Reciprocal inhibition across the spinal cord
cause alternate sides to contract.
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Ch. 16 Upper Motor Neuron Control
• Posture: vestibular nuclei & reticular
formation --> terminal zones in medial spinal
cord.
• Precise movements of distal parts of limbs:
motor cortex --> terminal fields in the lateral
parts of the spinal cord gray matter in a few
spinal cord segments
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Upper motor neuron
• Gives rise to a descending projection
that controls the activity of lower motor
neurons in the brain stem and the spinal
cord.
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Brainstem structures
• Influence of lower motor neurons to
neck muscles: superior colliculus axons
project to medial cell groups in the
cervical cord. These generate head
orienting movements.
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• Red nucleus axons: together with lateral
corticospinal tract axons
– --> control arms.
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Brainstem
• Upper motor neurons for balance and
posture
– Vestibular nuclei are upper motor neurons
with descending axons that terminate in
the medial region of the spinal cord gray
matter.
– Information from cranial nerve VIII (inner
ear)
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Pathways through vestibular nuclei
• Cranial nerve VIII
--> vestibular nuclei
--> descending axons
--> Lateral vestibular tract: most
terminate in medial region of spinal
cord. OR
Medial vestibular tract: some extend
laterally to contact muscles.
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Pathways through vestibular nuclei
• Also, pathways from upper motor
neurons to lower motor neurons that
control eye movements.
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Reticular Formation
• Network of circuits
• Located at the brainstem core, from midbrain
to medulla.
• Descending motor control pathways to the
spinal cord
- terminate primarily in the medial parts of the
gray matter where they influence the local
circuit neurons that co-ordinate axial and
proximal limb muscles.
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Reticular formation: functions
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cardiovascular & respiratory control.
sensory motor reflexes
org. of eye movements
regulate sleep and wakefullness
* temporal and spatial co-ordination of
movement
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Posture
• In response to disturbances in body
position (env or self)
– -->Vestibular nuclei and reticular formation
– --> information to the spinal cord
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Vestibular nuclei
response from inner ear to change in balance
Inner ear
Vestibular nuclei
Direct projections to the spinal cord
Compensation in stability
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Adjustments to stabilize posture during ongoing
movements
• Motor centers in cortex or brain stem
reticular formation
Appropriate neurons are activated
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Feedforeward
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