MOTOR SYSTEMS: SPINAL CORD D. C. MIKULECKY PROFESSOR OF PHYSIOLOGY AND FACULTY MENTORING PROGRAM

GENERAL FEATURES OF THE MOTOR SYSTEM zHIERARCHICAL ORGANIZATION zVS zPARALLEL ORGANIZATION

HIERARCHICAL ORGANIZATION MOTOR CORTEX CEREBELLUM AND BASAL GANGLIA BRAIN STEM SPINAL CORD SKELETAL MUSCLE

PARALLEL ORGANIZATION MOTOR CORTEX SKELETAL MUSCLE BRAIN STEM SPINAL CORD

MUSCLES AND NERVES zSKELETAL MUSCLE zTHE MOTOR UNIT zTHE CODING OF CONTRACTILE FORCE

SKELETAL MUSCLE: ANATOMICAL FEATURES zEXTRAFUSAL FIBERS: MULTINUCLEATE CELLS WHICH ARE THE MAIN CONTRACTILE ELEMENTS zINTRAFUSAL FIBERS: SENSING AND CONTROL OF THE CONTRACTING MUSCLE zMUSCLE: MANY PARALLEL FIBERS

SKELETAL MUSCLE: ANTAGONISTIC ARRANGEMENT zALL MUSCLES ATTACHED TO BONE AT BOTH ENDS (ORIGIN AND INSERTION) zUSUALLY ARRANGED IN ANTOGONISTIC PAIRS (FLEXORS AND EXTENSORS)

THE MOTOR UNIT zA SINGLE MOTOR NEURON AND ALL THE MUSCLES IT INNERVATES zTHE FUNCTIONAL UNIT OF THE MOTOR SYSTEM zCORRESPONDS TO THE SENSORY UNIT/RECEPTIVE FIELD RELATIONSHIP zSIZE OF MOTOR UNIT DETERMINES FINENESS OF MOTOR RESPOSE

THE CODING OF CONTRACTILE FORCE zFREQUENCY CODING: HIGHER FREQUENCY OF INCOMING ACTION POTENTIALS GENERATES MORE FORCE zPOPULATION CODING: MORE UNITS RECRUITED TO GET MORE FORCE

THE MOTOR RESPONSE SYSTEM: SPINAL LEVEL zTHE ORGANIZATION OF MOTOR NERVES IN THE SPINAL COLUMN zTHE ROLE OF INTERNEURONS zTHE ROLE OF LOCOMOTOR GENERATORS

THE ORGANIZATION OF MOTOR NERVES IN THE SPINAL COLUMN zDORSAL AREA OF VENTRAL HORN: FLEXOR MOVEMENTS zVENTRAL AREA OF VENTRAL HORN: EXTENSOR MOVEMENTS zDORSOLATERAL AREA OF VENTRAL HORN: INNERVATE EXTREMITIES zVENTROMEDIAL REGION: AXIAL MUSCLES TO MAINTAIN POSTURE

LOCATION OF CELL BODIES FOR EXTENSORS AND FLEXORS FLEXORS EXTENSORS

THE ROLE OF INTERNEURONS zLOCATED IN THE INTER MEDIATE ZONE OF THE SPINAL CORD zLATERAL SIDE NEURONS SYNAPSE IPSILATERALLY (TO DISTAL LIMB MUSCLES) zMIDLINE NEURONS SYNAPSE BOTH SIDES (MUSCLES FOR POSTURE) ALPHA MOTOR NEURONS:EXCITE SYNERGISTIC AND INHIBIT ANTAGONISTIC

THE ROLE OF LOCOMOTOR GENERATORS zRHYTHMIC ACTION OF ALTERANATING FLEXION AND EXTENSION INVOVED IN WALKING MOVEMENTS (CHICKEN WITH ITS HEAD CUT OFF) zSPINAL TRANSECTED ANIMALS CAN WALK ON TREADMILL zUNDER CONTROL OF LOCOMOTOR COMMAND CENTER IN THE BRAIN STEM

SENSORY FIBERS IN THE MUSCLE zTHE MUSCLE SPINDLE AS LENGTH DETECTOR zGOGLI TENDON ORGANS: TENSION RECEPTORS

THE MUSCLE SPINDLE AS LENGTH DETECTOR(SENSORY FIBERS) zTYPE Ia NERVE FIBERS: TRANSMIT INFORMATION ABOUT LENGTH AND VELOCITY TO THE CNS zTYPE II NERVE FIBERS:TRANSMIT INFORMATION ABOUT MUSCLE LENGTH TO CNS z

TWO TYPES OF INTRAFUSAL FIBERS NUCLEAR CHAIN FIBER NUCLEAR BAG FIBER TYPE II SENSORY FIBER TYPE IA SENSORY FIBER

TWO TYPES OF MOTOR NEURON zALPHA MOTOR NEURON: INNERVATES EXTRAFUSAL FIBER zGAMMA MOTOR NEURON: INNERVATES INTRAFUSAL FIBERS

STRETCHING AN INTRAFUSAL FIBER SENDS SIGNALS TO CNS

THE ROLE OF GAMMA MOTOR NEURONS IN REGULATING MUSCLE SPINDLE RESPONSE RECORD STIMULATE Afferent Activity Muscle Force

THE ROLE OF GAMMA MOTOR NEURONS IN REGULATING MUSCLE SPINDLE RESPONSE RECORD STIMULATE Afferent Activity Muscle Force STIMULATE

GOGLI TENDON ORGANS: TENSION RECEPTORS zIN SERIES WITH EXTRAFUSAL FIBERS zTRANSMITS INFORMATION ABOUT FORCE OR TENSION TO CNS zFREQUENCCY CODING

SPINAL REFLEXES zTHE STRETCH REFLEX zTHE INVERSE MYOTACTIC REFLEX zTHE FLEXOR WITHDRAWAL REFLEX

THE STRETCH REFLEX (KNEE JERK REFLEX) zTAP PATELLAR TENDON BELOW KNEE zSENSORY SIGNALS FROM MUSCLE SPINDLE INDICATE FLEXION OF LEG zFLEXOR IS INHIBITED zEXTENSOR ACTIVATED zLEG EXTENDS

KNEE JERK REFLEX SPINAL CORD SENSORY NEURON FROM MUSCLE SPINDLE DETECTS STRETCH FLEXOR INHIBITED EXTENSOR ACTIVATED

THE INVERSE MYOTACTIC REFLEX zDETECTION OF EXCESS WEIGHT BY GOGLI TENDON ORGAN zINHIBIT FLEXOR (BICEPS) zACTIVATE EXTENSOR

INVERSE MYOTACTIC REFLEX ARM FLEXED WEIGHT TOO HEAVY BICEPS & SYNERGYSTIC MUSCLE CONTRACTED EXTENSOR RELAXED TENDON STRETCHED

INVERSE MYOTACTIC REFLEX ARM EXTENDS WEIGHT RELEASED BICEPS & SYNERGYSTIC MUSCLE RELAXEDEXTENSOR CONTRACTED

THE FLEXOR WITHDRAWAL REFLEX zPAINFUL STIMULUS DETECTED zIPSILATERAL EXTENSORS INHIBITED zIPSILATERAL EXTENSORS EXCITED zLIMB IS WITHDRAWN zIF 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