MOTOR SYSTEMS: SPINAL CORD

D. C. MIKULECKYPROFESSOR OF PHYSIOLOGY

ANDFACULTY MENTORING PROGRAM

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

SKELETAL MUSCLE

BRAIN STEM

SPINAL CORD

MUSCLES AND NERVES

SKELETAL MUSCLE

THE MOTOR UNIT

THE CODING OF CONTRACTILE FORCE

SKELETAL MUSCLE: ANATOMICAL FEATURES

EXTRAFUSAL FIBERS: MULTINUCLEATE CELLS WHICH ARE THE MAIN CONTRACTILE ELEMENTS

INTRAFUSAL FIBERS: SENSING AND CONTROL OF THE CONTRACTING MUSCLE

MUSCLE: MANY PARALLEL FIBERS

SKELETAL MUSCLE: ANTAGONISTIC ARRANGEMENT

ALL MUSCLES ATTACHED TO BONE AT BOTH ENDS (ORIGIN AND INSERTION)

USUALLY ARRANGED IN ANTOGONISTIC PAIRS (FLEXORS AND EXTENSORS)

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

THE CODING OF CONTRACTILE FORCE

FREQUENCY CODING: HIGHER FREQUENCY OF INCOMING ACTION POTENTIALS GENERATES MORE FORCE

POPULATION CODING: MORE UNITS RECRUITED TO GET MORE FORCE

THE MOTOR RESPONSE SYSTEM: SPINAL LEVEL

THE ORGANIZATION OF MOTOR NERVES IN THE SPINAL COLUMN

THE ROLE OF INTERNEURONSTHE 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 STEM

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

NUCLEARCHAIN

FIBER

NUCLEARBAGFIBER

TYPE IISENSORYFIBER

TYPE IASENSORYFIBER

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

RECORD

RECORD

STIMULATE

Afferent Activity

Muscle Force

THE ROLE OF GAMMA MOTOR NEURONS IN REGULATING MUSCLE SPINDLE RESPONSE

RECORD

RECORD

STIMULATE

Afferent Activity

Muscle Force

STIMULATE

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 INHIBITEDEXTENSOR ACTIVATEDLEG EXTENDS

KNEE JERK REFLEX

SPINALCORD

SENSORY NEURON FROMMUSCLE SPINDLE DETECTSSTRETCH

FLEXOR INHIBITED

EXTENSORACTIVATED

THE INVERSE MYOTACTIC REFLEX

DETECTION OF EXCESS WEIGHT BY GOGLI TENDON ORGAN

INHIBIT FLEXOR (BICEPS)

ACTIVATE EXTENSOR

INVERSE MYOTACTIC REFLEX

ARM FLEXED

WEIGHTTOOHEAVY

BICEPS & SYNERGYSTIC MUSCLECONTRACTED EXTENSOR RELAXEDTENDON STRETCHED

INVERSE MYOTACTIC REFLEX

ARM EXTENDS

WEIGHTRELEASED

BICEPS & SYNERGYSTIC MUSCLERELAXEDEXTENSOR CONTRACTED

THE FLEXOR WITHDRAWAL REFLEX

PAINFUL STIMULUS DETECTEDIPSILATERAL EXTENSORS INHIBITEDIPSILATERAL EXTENSORS EXCITEDLIMB IS WITHDRAWNIF INVOLVING ONE FOOT WHILE

STANDING, CONTRALATERAL SIDE EXTENSORS ACTIVATED AND FLEXORS INHIBITED TO SUPPORT GREATER WEIGHT

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