motor system cerebral cortex
TRANSCRIPT
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Motor System
The cerebral cortex
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1.Sensory perception2.Voluntary control of movement3.Language4.Personality traits5.Sophisticated mental events,such as
thinking memory, decision making, creativity, and self-consciousness
Brain component
Major Functions Cerebral cortex
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Figure 5.9Page 146Frontallobe
Central sulcus
Parietallobe
Parietooccipitalnotch
Occipitallobe
Preoccipitalnotch
CerebellumBrain stem
Temporallobe
Lateralfissure
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FrontLefthemisphere
Primarymotorcortex
Topview
Somato-sensorycortex
Righthemisphere
Frontallobe
Centralsulcus
Parietallobe
Occipital lobe
Back
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Figure 5.10Page 147
Centralsulcus Posterior
parietal cortex
Wernicke’s area
Parietal-temporal-occipitalassociation cortex
Primary visual cortex
Cerebellum
Limbic associationcortex
Primary auditory cortex
Broca’s area
PrefrontalAssociationcortex
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Supplementary motor area
Primary motor cortex Somatosensory cortex
Posterior parietal cortex
Wernicke’s area
Parietal-temporal-occipitalassociation cortex
Primary visual cortex
Brain stem
Limbic associationcortex
Primary auditory cortex
Broca’s area
Premotor cortex
PrefrontalAssociationcortex
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The sensorimotor cortex
Posterior Parietal
5,7
S1
3,1,2M1
4
PMA6
SMA6
Signals converge onto the primary
motor cortexBrainstem &Spinal cord
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Sensory input
Primary sensory areas (somatosensory,
visual, auditory cortices)
Higher sensory areas
Association areas
Higher motor areas
Primary motor areas
Motor output
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Supplementary motor area (secondary motor cortex (6 & 8): programming of complex movements (both sides)
Primary motor cortex (M1;area4): voluntary movement
Premotor cortex (6): coordination of complex movements, important in orienting the body and arms toward a specific target
Prefrontal AssociationCortex: planning for voluntary activity; decision making; creativity and personality traits
Supplementary motor area, Premotor cortex, Prefrontal Association Cortex command the primary motor cortex
Does not itself initiate voluntary
movement
The idea of a voluntary
movement
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Supplementary motor area: stimulation complex patterns of movements e.g., hand open/ close. Lesions do not lead to paralysis but to Motor apraxia.
Primary motor cortex: Lesions lead to paralysis/Paresis (weakness), clumsinessand slowness of movement
Premotor cortex: works in association with posterior parietal cortex. Damage inability to process complex sensory information to accomplish purposeful movement in space.
Prefrontal AssociationCortex: deficits changes in personality and social behaviour
Motor apraxia: loss of learned motor skills
without paralysis
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Figure 5.12 (2)Page 149
Lefthemisphere
Cross-sectional view
Temporal lobe
Motor homunculus
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The upper part of the face is bilaterally represented but the rest of the body is represented unilaterally
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Figure 5.11 (2)Page 149
Lefthemisphere
Cross-sectional view
Temporal lobe
Sensory homunculus
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How M1 commands voluntary movement?
• Much of motor cortex is active for every movement
• Activity of each cell represents a single vote for a particular direction of movement
• Direction of movement is determined by a tally and averaging of the votes registered by each cell in the population
• The larger the population representing a type of movement, the finer the possible control.
M1 is organized in terms of movements rather than muscles
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Parameters of movement controlled by M1 (area 4)
• Direction– neurons
• Speed:– neurons
• Force:– Firing rate of neurons
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Figure 5.13Page 152
Facial area ofmotor cortex
Broca’sarea
Bundle ofinterconnecting fibers
Wernicke’sarea
Visual cortex
Angular gyrus of
parietal-temporal-occipitalassociation cortex
Motor speech area
Sensory speech area
1
2
3
4
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Descending Tracts
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Corticospinal tract
Lateral pathways Medial pathways
Major descending spinal tracts and their points of origin
Cerebral cortex
Vestibular Nucleus and
superior colliculus
Red nucleus
Reticular nuclei
Spinal cord
Rubrospinal tract
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The lateral system
• Includes the lateral corticospinal tract and part of the corticobulbar tract + rubrospinal tracts.
• These pathways influence contra lateral motor neurons that supply the musculature of the limbs, especially the digits, the muscles of the lower face, and the tongue.
• Controls fine discrete movements• Inhibitory to muscle tone and reflexes
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The medial system (ventromedial system)
• Includes the – ventral corticospinal, – lateral and medial vestibulospinal, – pontine and medullary reticulospinal,– tectospinal tracts.
• These pathways mainly– affect posture, and – provide the motor background for movements of the
limbs and digits.– Involved in locomotion
• Modulates the skeletal muscle tone (excitatory and inhibitory)
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Pathways that originate in the brainstem influence
• posture,
• locomotion, and
• eye movements.
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Influences of the brain stem centers on spinal reflexes
(alpha and gamma extensor and flexor motor neurons)
• Lateral vestibular nucleus extensor activity
• Pontine reticular Formation extensor activity• Red nucleus flexor activity• Medullary reticular Formation flexor activity
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Relationship of the thalamus, basal ganglia, and cortex in the control of movement
Cerebral cortex
Pontine RF
Vestibular nucleus Medullary RF
Spinal cord+ +
+
-+/-
-
-
-
Antigravity muscles
A high degree of natural excitability
Basal ganglia:Inhibit muscle
tone
Cerebellum:enhance
muscle tone
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Role of cortex and other structures in the control of movement
Cerebral cortex
Pontine RF
Vestibular nucleus Medullary RF
Spinal cord+ +
+
-+/-
-
-
-
Decorticate spasticity
Decerebrate rigidity
Flaccid
Antigravity muscles
A high degree of natural excitability