MOTOR SYSTEMS: THE BRAIN

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MOTOR SYSTEMS THE BRAIN

• D. C. MIKULECKY
• PROFESSOR OF PHYSIOLOGY
• AND
• FACULTY MENTORING PROGRAM

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CONTROL OF POSTURE BY THE BRAIN STEM

• THE VENTROMEDIAL PATHWAY
• THE LATERAL RETICULOSPINAL TRACT
• THE RUBROSPINAL TRACTH

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BRAIN STEM CENTERS FOR MOTOR CONTROL
TECTUM
LATERAL RETICULAR FORMATION
RED NUCLEUS
MEDIAL RETICULAR FORMATION
LATERAL AND MEDIAL VESTIBULAR NUCLEI
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THE VENTROMEDIAL PATHWAY

• VESTIBULOSPINAL TRACT CARRIES INFORMATION FROM
  VESTIBULAR NUCLEUS FOR REFLEX CONTROL OF
  EQUILIBRIUM
• TECTOSPINAL TRACT ORIGINATES IN TECTUM FOR
  CONTROL OF HEAD AND EYE MOVEMENTS
• MEDIAL RETICULOSPINAL TRACT ORIGINATES IN
  RETICULAR FORMATION FOR MAINTAINING POSTURE BY
  ACTIVATION OF EXTENSORS

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PATHWAYS FROM BRAINSTEM FOR MOTOR CONTROL
VENTROMEDIAL
TECTO- SPINAL TRACT
VESTIBULO- SPINAL TRACTS
RETICULO- SPINAL TRACT
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LOCATION OF CELL BODIES FOR EXTENSORS AND FLEXORS
FLEXORS

EXTENSORS
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THE LATERAL RETICULOSPINAL TRACT

• FROM LATERAL RETICULAR NUCLEUS
• DESCEND IN LATERAL REGION OF THE SPINAL CORD

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PATHWAYS FROM BRAINSTEM FOR MOTOR CONTROLLATERAL
RETICULOSPINAL TRACT
LATERAL RETICULO- SPINAL TRACT
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THE RUBROSPINAL TRACTH

• FIBERS ORIGINATE IN RED NUCLEUS
• DESCEND ALONG DORSAL AND LATERAL BORDERS OF CORD
• INNERVATE DISTAL FLEXOR MUSCLES

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PATHWAYS FROM BRAINSTEM FOR MOTOR CONTROL
RUBROSPINAL
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SUMMARY OF CONTROL OF SPINAL MOTOR NEURONS BY
BRAIN STEM
RUBRO- SPINAL TRACT
LATERAL RETICULO- SPINAL TRACT
(-)
(-)
()
(-)
()
TO FLEXORS
TO FLEXORS
TO EXTENSORS
VENTROMEDIAL PATHWAY
TO EXTENSORS
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THE MOTOR CORTEX

• ORGANIZATION
• DESCENDING PATHWAYS
• SENSORY FEEDBACK
• CORTICAL CODING OF REACHING MOVEMENTS

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ORGANIZATION OF THE MOTOR CORTEX

• CORTICAL EFFERENT ZONES VERTICAL COLUMNS OF
  CELLS
• EACH ZONE CONTROLS ONE MUSCLE
• SIX DIFFERENT LAYERS OF CELLS
• OUTPUT LAYER IS LAYER V
• EXCITE BOTH ALPHA AND GAMMA MOTOR NEURONS

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CORTICAL AREAS INVOVED IN MOTOR CONTROL
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SOMATOTOPIC ORGANIZATION OF THE MOTOR CORTEX
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DESCENDING PATHWAYS FROM THE MOTOR CORTEX

• CORTICOSPINAL PATHWAY
• CORTICOBULBAR PATHWAY
• PYRAMIDAL TRACT
• LATERAL CORTICOSPINAL TRACT

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PATHWAYS FROM CORTEX FOR MOTOR CONTROL LATERAL
CORTICOSPINAL TRACT
PREMOTOR AREA
LATERAL CORTICO- SPINAL TRACT
DORSAL COLUMN NUCLEI
RED NUCLEUS
1 2 3
4
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PRIMARY MOTOR CORTEX
PYRAMIDAL TRACT
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PATHWAYS FROM CORTEX FOR MOTOR CONTROL
CORTICOSPINAL TRACTS
PREMOTOR AREA
LATERAL CORTICO- SPINAL TRACT
DORSAL COLUMN NUCLEI
RED NUCLEUS
1 2 3
4
6
VENTRAL CORTICO- SPINAL TRACT
PRIMARY MOTOR CORTEX
PYRAMIDAL TRACT
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SENSORY FEEDBACK TO THE MOTOR CORTEX

• VIA SOMATIC SENSORY CORTEX
• CONNECTED IN A TOPOGRAPHIC MANNER
• MONITOR MOVEMENT AND SMOOTH AND CORRECT

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CORTICAL CODING OF REACHING MOVEMENTS

• DYNAMIC NEURONS CODE FOR RATE OF FORCE
  DEVELOPMENT
• STEADY STATE FORCE
• NEURONS CONTROLLING RATE AND DIRECTION OF
  MOVEMENT ARE DISTRIBUTED (NO ONE NEURON HAS ALL
  THE INFORMATION)

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SUPPLIMENTAL MOTOR AREAS PROGRAM MOVEMENT

• HYPOTHALAMUS INVOLVED IN MOTIVATIONAL FACTORS
• TRANSMIT INFORMATION TO SUPPLIMENTAL AND PREMOTOR
  CORTEX
• HERE THE DESIGN OF THE MOVEMENT IS EXECUTED
• REHERSAL OF MOVEMENTS AS WELL

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POSTERIOR PARIETAL CORTEX INTEGRATES SENSORY
STIMULI FOR PURPOSEFUL MOVEMENT

• RECEIVES BOTH SOMATIC AND VISUAL SENSORY
  INFORMATION
• TRANSMITS IT TO SUPPLIMENTAL AND PREMOTOR AREAS

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CORTICAL AREAS INVOVED IN MOTOR CONTROL