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EXTRAPYRAMIDAL SYSTEM
KINNARI THACKER
ROLL NO:132
INTRODUCTION
• THE MOTOR PATHWAYS ARE THE DESCENDING TRACTS.
• INCLUDES TWO MAIN TRACTS:i. PYRAMIDAL TRACTS.ii. EXTRAPYRAMIDAL TRACTS.
EXTRAPYRAMIDAL TRACTS
• DESCENDING TRACTS OTHER THAN PYRAMIDAL TRACTS IN THE SPINAL CORD ARE COLLECTIVELY CALLED EXTRAPYRAMIDAL TRACTS.
CONT…
• INCLUDES:i. RUBROSPINAL TRACT.ii. TECTOSPINAL TRACT.iii. VESTIBULOSPINAL TRACT.iv. RETICULOSPINAL TRACT.v. MEDIAL LONGITUDINAL FASCICULUS.
RUBROSPINAL TRACT• ORIGIN: RED NUCLEUS OF MIDBRAIN.• COURSE: IMMEDIATELY AFTER ORIGIN THESE
FIBRES CROSS TO THE OPPOSITE SIDE--> DESCENDS THROUGH PONS AND MEDULLA .
• TERMINATION: MAINLY ON THE INTERNEURONS.
CONT…• FUNCTION: - EXHIBITS FACILITATORY INFLUENCE ON FLEXOR MUSCLES AND
INHIBITORY INFLUENCE ON THE EXTENSORS.
VESTIBULOSPINAL TRACTS
• THERE ARE TWO VESTIBULOSPINAL TRACTS:i. LATERAL VESTIBULOSPINAL TRACTii. MEDIAL VESTIBULOSPINAL TRACT
LATERAL VESTIBULOSPINAL TRACT
• ORIGIN: LATERAL VESTIBULAR NUCLEUS.• COURSE: THESE FIBRES ARE UNCROSSED AND
LIES IN THE ANTERIOR FUNICULUS OF SPINAL CORD SHIFTING MEDIALLY AS IT DESCENDS.
• TERMINATION: EXTEND UPTO CAUDAL SEGMENTS OF CORD AND TERMINATE INTO NEURONS OF VENTRAL GREY COLUMN.
CONT….• FUNCTIONS:- MAINLY FACILITATES
ACTIVITY OF EXTENSOR MUSCLES AND INHIBITS THE ACTIVITY OF FLEXOR MUSCLES IN
ASSOCIATION WITH THE MAINTENANCE OF
BALANCE.
MEDIAL VESTIBULOSPINAL TRACT
• ORIGIN: MEDIAL VESTIBULAR NUCLEUS.• COURSE: DESCENDS THROUGH THE ANTERIOR
FUNICULUS.• TERMINATION: END IN THE ANTERIOR MOTOR
NEURONS DIRECTLY OR THROUGH INTERNUNCIAL NEURONS OF CERVICAL SEGMENTS OF SPINAL CORD.
CONT…• FUNCTION:- DONOR CONNECTION OF
MEDIAL LONGITUDINAL FASCICULUS.
- PROVIDES A REFLEX PATHWAY FOR MOVEMENTS OF HEAD, NECK, AND EYES IN RESPONSE TO VISUAL AND AUDITORY STIMULI.
RETICULOSPINAL TRACT
• THRE ARE TWO RETICULOSPINAL TRACTS:i. MEDIAL(PONTINE) RETICULOSPINAL TRACT.ii. LATERAL(MEDULLARY) RETICULOSPINAL
TRACT.
MEDIAL RETICULOSPINAL TRACT
• ORIGIN: MEDIAL PONTINE RETICULAR FORMATION.
• COURSE: ANTERIOR FUNICULUS OF SPINAL CORD
• TERMINATION: IN THE LAMINA OF SPINAL GREY MATTER AND THROUGH INTERNUNCIAL NEURONS INFLUENCE ALPHA AND GAMMA NEURONS
CONT…• FUNCTIONS:- EXCITATORY TO
ANTIGRAVITY MUSCLES- FACILITATE CONTROL OF
VOLUNTARY AND REFLEX MOVEMENTS AND CONTROL OF MUSCLE TONE
- FAVOURS EXPIRATION- VASOCONSTRICTION
LATERAL RETICULOSPINAL
• ORIGIN: MEDULLARY RETICULAR FORMATION.• COURSE: DESCENDS IN LATERAL FUNICULUS
MEDIAL TO LATERAL CORTICOSPINAL AND RUBROSPINAL TRACTS.
• TERMINATION: INTERNUNCIAL NEURONS OF LAMINAE OF SPINAL CORD.
CONT…• FUNCTIONS:- INHIBITORY TO
ANTIGRAVITY MUSCLES.- INHIBIT CONTROL OF
VOLUNTARY AND REFLEX MOVEMENTS AND MUSCLE TONE.
- FAVOURS INSPIRATION.- VASODILATATION.
TECTOSPINAL TRACT
• ORIGIN: SUPERIOR COLLICULUS• COURSE: DESCENDS THROUGH PONS AND
MEDULLA INTO THE ANTERIOR WHITE FUNICULUS OF THE SPINAL CORD
• TERMINATION: UPPER CERVICAL LEVELS BY SYNAPSING ON THE ANTERIOR HORN CELL.
CONT…• FUNCTION:- MOTOR LIMB OF THE
REFLEX PATHWAY IN RESPONSE TO VISUAL, HEARING OR OTHER EXTEROCEPTIVE STIMULI.
MEDIAL LONGITUDINAL FASCICULUS
• ORIGIN: MEDIAL VESTIBULAR NUCLEUS RETICULAR FORMATION SUPERIOR COLLICULUS INTERSTITIAL NUCLEUS CAJAL• COURSE: DESCENDS UPTO UPPER CERVICAL
REGION.• TERMINATION: VENTRAL HORN CELLS THAT
INNERVATE MUSCLE OF THE NECK.
CONT…
• FUNCTION:- COORDINATION OF
REFLEX OCULAR MOVEMENTS
- INTEGRATION OF EYE AND NECK MOVEMENTS.
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