control of muscle movement d. c. mikulecky department of physiology
TRANSCRIPT
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CONTROL OF MUSCLE MOVEMENT
D. C. MIKULECKY
DEPARTMENT OF PHYSIOLOGY
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SPINAL CORDDORSAL HORN GREY
MATTER
DORSAL
VENTRAL
SPINAL NERVE
DORSALROOTGANGLION
VENTRALHORN
WHITEMATTER
LATERAL
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SEGMENTAL STRUCTURE OF SPINAL NERVES
DERMATOMES
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THE THALAMUS IN SOMATIC SENSATION
DORSAL COLUMN
MEDULLA
MEDIALLEMNISCUS
SENSORYNEOCORTEX
DORSAL COLUMNNUCLEI
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SOMATOTOPIC ORGANIZATION OF THE SENSORY CORTEX
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GENERAL FEATURES OF THE MOTOR SYSTEM
• HIERARCHICAL ORGANIZATION
• VS
• PARALLEL ORGANIZATION
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HIERARCHICAL ORGANIZATION
MOTOR CORTEX
CEREBELLUM AND BASAL GANGLIA
BRAIN STEM
SPINAL CORD
SKELETAL MUSCLE
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PARALLEL ORGANIZATIONMOTOR CORTEX
SKELETAL MUSCLE
BRAIN STEM
SPINAL CORD
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THE MOTOR UNIT
• A SINGLE MOTOR NEURON AND ALL THE MUSCLES IT INNERVATES
• THE FUNCTIONAL UNIT OF THE MOTOR SYSTEM
• CORRESPONDS TO THE SENSORY UNIT/RECEPTIVE FIELD RELATIONSHIP
• SIZE OF MOTOR UNIT DETERMINES FINENESS OF MOTOR RESPOSE
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SOMATOTOPIC ORGANIZATION OF THE MOTOR CORTEX
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CORTICAL AREAS INVOVED IN MOTOR CONTROL
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THE MOTOR RESPONSE SYSTEM: SPINAL LEVEL
• THE ORGANIZATION OF MOTOR NERVES IN THE SPINAL COLUMN
• THE ROLE OF INTERNEURONS
• THE ROLE OF LOCOMOTOR GENERATORS
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THE ORGANIZATION OF MOTOR NERVES IN THE SPINAL COLUMN
• DORSAL AREA OF VENTRAL HORN: FLEXOR MOVEMENTS
• VENTRAL AREA OF VENTRAL HORN: EXTENSOR MOVEMENTS
• DORSOLATERAL AREA OF VENTRAL HORN: INNERVATE EXTREMITIES
• VENTROMEDIAL REGION: AXIAL MUSCLES TO MAINTAIN POSTURE
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LOCATION OF CELL BODIES FOR EXTENSORS AND FLEXORS
FLEXORS
EXTENSORS
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THE ROLE OF INTERNEURONS
• LOCATED IN THE INTER MEDIATE ZONE OF THE SPINAL CORD
• LATERAL SIDE NEURONS SYNAPSE IPSILATERALLY (TO DISTAL LIMB MUSCLES)
• MIDLINE NEURONS SYNAPSE BOTH SIDES (MUSCLES FOR POSTURE) ALPHA MOTOR NEURONS:EXCITE SYNERGISTIC AND INHIBIT ANTAGONISTIC
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THE ROLE OF LOCOMOTOR GENERATORS
• RHYTHMIC ACTION OF ALTERANATING FLEXION AND EXTENSION INVOVED IN WALKING MOVEMENTS (CHICKEN WITH ITS HEAD CUT OFF)
• SPINAL TRANSECTED ANIMALS CAN WALK ON TREADMILL
• UNDER CONTROL OF LOCOMOTOR COMMAND CENTER IN THE BRAIN STEM
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SENSORY FIBERS IN THE MUSCLE
• THE MUSCLE SPINDLE AS LENGTH DETECTOR
• GOGLI TENDON ORGANS: TENSION RECEPTORS
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THE MUSCLE SPINDLE AS LENGTH
DETECTOR(SENSORY FIBERS) • TYPE Ia NERVE FIBERS: TRANSMIT
INFORMATION ABOUT LENGTH AND VELOCITY TO THE CNS
• TYPE II NERVE FIBERS:TRANSMIT INFORMATION ABOUT MUSCLE LENGTH TO CNS
•
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TWO TYPES OF INTRAFUSAL FIBERS
NUCLEARCHAIN
FIBER
NUCLEARBAGFIBER
TYPE IISENSORYFIBER
TYPE IASENSORYFIBER
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TWO TYPES OF MOTOR NEURON
• ALPHA MOTOR NEURON: INNERVATES EXTRAFUSAL FIBER
• GAMMA MOTOR NEURON: INNERVATES INTRAFUSAL FIBERS
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STRETCHING AN INTRAFUSAL FIBER SENDS SIGNALS TO CNS
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THE ROLE OF GAMMA MOTOR NEURONS IN REGULATING MUSCLE SPINDLE RESPONSE
RECORD
RECORD
STIMULATE
Afferent Activity
Muscle Force
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THE ROLE OF GAMMA MOTOR NEURONS IN REGULATING MUSCLE SPINDLE RESPONSE
RECORD
RECORD
STIMULATE
Afferent Activity
Muscle Force
STIMULATE
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GOGLI TENDON ORGANS: TENSION RECEPTORS
• IN SERIES WITH EXTRAFUSAL FIBERS
• TRANSMITS INFORMATION ABOUT FORCE OR TENSION TO CNS
• FREQUENCCY CODING
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SPINAL REFLEXES
• THE STRETCH REFLEX
• THE INVERSE MYOTACTIC REFLEX
• THE FLEXOR WITHDRAWAL REFLEX
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THE STRETCH REFLEX (KNEE JERK REFLEX)
• TAP PATELLAR TENDON BELOW KNEE
• SENSORY SIGNALS FROM MUSCLE SPINDLE INDICATE FLEXION OF LEG
• FLEXOR IS INHIBITED
• EXTENSOR ACTIVATED
• LEG EXTENDS
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KNEE JERK REFLEX
SPINALCORD
SENSORY NEURON FROMMUSCLE SPINDLE DETECTSSTRETCH
FLEXOR INHIBITED
EXTENSORACTIVATED
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INVERSE MYOTACTIC REFLEX
ARM EXTENDS
WEIGHTRELEASED
BICEPS & SYNERGYSTIC MUSCLERELAXEDEXTENSOR CONTRACTED
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THE FLEXOR WITHDRAWAL REFLEX
• PAINFUL STIMULUS DETECTED• IPSILATERAL EXTENSORS INHIBITED• IPSILATERAL EXTENSORS EXCITED• LIMB IS WITHDRAWN• IF INVOLVING ONE FOOT WHILE
STANDING, CONTRALATERAL SIDE EXTENSORS ACTIVATED AND FLEXORS INHIBITED TO SUPPORT GREATER WEIGHT
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FLEXOR WITHDRAWAL REFLEX
STEPON TACK
SENSORYSIGNAL TO SPINE
VIAINTERNEURONS
IPSILATERAL EXTENSORS INHIBITEDIPSILATERAL FLEXORS CONTRACT-LEG LIFTSCONTRALATERAL EXTENSORS CONTRACTCONTRALATERAL FLEXORS INHIBITED- MAINTAIN BALANCE AND SUPPORT WEIGHT