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CONTROL OF MUSCLE MOVEMENT D. C. MIKULECKY DEPARTMENT OF PHYSIOLOGY SPINAL CORD DORSAL HORN DORSAL DORSAL ROOT GANGLION SPINAL NERVE GREY MATTER LATERAL WHITE MATTER VENTRAL HORN VENTRAL SEGMENTAL STRUCTURE OF SPINAL NERVES DERMATOMES THE THALAMUS IN SOMATIC SENSATIONSENSORY NEOCORTEX MEDIAL LEMNISCUS DORSAL COLUMN NUCLEI DORSAL COLUMN MEDULLA SOMATOTOPIC ORGANIZATION OF THE SENSORY CORTEX GENERAL FEATURES OF THE MOTOR SYSTEM • HIERARCHICAL ORGANIZATION • VS • PARALLEL ORGANIZATION HIERARCHICAL ORGANIZATION MOTOR CORTEX CEREBELLUM AND BASAL GANGLIA BRAIN STEM SPINAL CORD SKELETAL MUSCLE PARALLEL ORGANIZATION MOTOR CORTEX BRAIN STEM SPINAL CORD SKELETAL MUSCLE 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 SOMATOTOPIC ORGANIZATION OF THE MOTOR CORTEX CORTICAL AREAS INVOVED IN MOTOR CONTROL THE MOTOR RESPONSE SYSTEM: SPINAL LEVEL • THE ORGANIZATION OF MOTOR NERVES IN THE SPINAL COLUMN • THE ROLE OF INTERNEURONS • THE ROLE OF LOCOMOTOR GENERATORS 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 LOCATION OF CELL BODIES FOR EXTENSORS AND FLEXORS FLEXORS EXTENSORS 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 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 SENSORY FIBERS IN THE MUSCLE • THE MUSCLE SPINDLE AS LENGTH DETECTOR • GOGLI TENDON ORGANS: TENSION RECEPTORS 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 • TWO TYPES OF INTRAFUSAL FIBERS TYPE IA SENSORY FIBER TYPE II SENSORY FIBER NUCLEAR CHAIN FIBER NUCLEAR BAG FIBER TWO TYPES OF MOTOR NEURON • ALPHA MOTOR NEURON: INNERVATES EXTRAFUSAL FIBER • GAMMA MOTOR NEURON: INNERVATES INTRAFUSAL FIBERS STRETCHING AN INTRAFUSAL FIBER SENDS SIGNALS TO CNS THE ROLE OF GAMMA MOTOR NEURONS IN REGULATING MUSCLE SPINDLE RESPONSE STIMULATE RECORD RECORD Afferent Activity Muscle Force THE ROLE OF GAMMA MOTOR NEURONS IN REGULATING MUSCLE SPINDLE RESPONSE STIMULATE RECORD STIMULATE RECORD Afferent Activity Muscle Force GOGLI TENDON ORGANS: TENSION RECEPTORS • IN SERIES WITH EXTRAFUSAL FIBERS • TRANSMITS INFORMATION ABOUT FORCE OR TENSION TO CNS • FREQUENCCY CODING SPINAL REFLEXES • THE STRETCH REFLEX • THE INVERSE MYOTACTIC REFLEX • THE FLEXOR WITHDRAWAL REFLEX 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 KNEE JERK REFLEX EXTENSOR ACTIVATED FLEXOR INHIBITED SENSORY NEURON FROM MUSCLE SPINDLE DETECTS STRETCH SPINAL CORD INVERSE MYOTACTIC REFLEX ARM EXTENDS WEIGHT RELEASED BICEPS & SYNERGYSTIC MUSCLE RELAXEDEXTENSOR CONTRACTED 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 FLEXOR WITHDRAWAL REFLEX STEPON TACK SENSORY SIGNAL TO SPINE VIA INTERNEURONS IPSILATERAL EXTENSORS INHIBITED IPSILATERAL FLEXORS CONTRACT-LEG LIFTS CONTRALATERAL EXTENSORS CONTRACT CONTRALATERAL FLEXORS INHIBITED- MAINTAIN BALANCE AND SUPPORT WEIGHT
