Dr Ahmed Fathalla Ibrahim CORTICOSPINAL TRACTS Concerned with

Dr. Ahmed Fathalla Ibrahim

CORTICOSPINAL TRACTS • Concerned with voluntary discrete & skilled movement, especially of distal parts of limbs • Formed of one neurone • Cells of origin: Large Betz cells in precentral gyrus (primary motor cortex)

CORTICOSPINAL TRACTS PATHWAY • Axons descend in : 1. Corona radiata 2. Posterior limb of internal capsule 3. Crus cerebri (middle 3/5) 4. Basis pontis 5. Pyramid of medulla

CORTICOSPINAL TRACTS LATERAL CORTICOSPINAL TRACT • Formed of 75 – 90% of fibers • Fibers decussate in the medulla (motor decussation) • Fibers descends in lateral white column of spinal cord • Fibers terminate in contralateral ventral horn cells of spinal cord

CORTICOSPINAL TRACTS VENTRAL CORTICOSPINAL TRACT • Formed of 10 – 25% of fibers • Fibers descend uncrossed in medulla • Fibers descends in ventral white column of spinal cord • Fibers decussate near to their termination in the spinal cord • Fibers terminate in contralateral ventral horn cells of spinal cord

CORTICOSPINAL TRACTS

RUBROSPINAL TRACTS • Cells of origin: red nucleus in midbrain • Receives afferents from motor cortex & cerebellum • Represents a route through which cerebral cortex & cerebellum can influence motor activity • Axons cross in ventral tegmental decussation

RUBROSPINAL TRACTS • Axons descend in lateral white column of spinal cord (Tract is ventrolateral & partly mixed with lateral corticospinal tract) • Axons terminate in contralateral ventral horn cells of spinal cord • The tract carries excitatory fibers to motor neurones of limb flexor muscles

RUBROSPINAL TRACTS

TECTOSPINAL TRACT • Cells of origin: superior colliculus in midbrain • Axons cross in dorsal tegmental decussation • Axons descend in ventral white column of spinal cord • Axons terminate in contralateral ventral horn cells of spinal cord • The tract mediates reflex movement in response to visual stimuli

VESTIBULOSPINAL TRACTS LATERAL VESTIBULOSPINAL TRACT • Cells of origin: lateral vestibular nucleus • Axons desend in ventral white column of spinal cord • Axons terminate in ipsilateral ventral horn cells of spinal cord • The tract mediates excitatory influences upon extensor motor neurones to maintain posture

VESTIBULOSPINAL TRACTS MEDIAL VESTIBULOSPINAL TRACT • Cells of origin: medial vestibular nucleus • Axons desend in ventral white column of spinal cord (as a part of medial longitudinal fasciculus) • Axons terminate in ipsilateral ventral horn cells of spinal cord • The medial longitudinal fasciculus consists of both ascending & descending fibers that link vestibular nuclei to nuclei supplying the extraocular muscles for coordination of head and eye movements

RETICULOSPINAL TRACTS MEDIAL RETICULOSPINAL TRACT • Cells of origin: pontine reticular formation • Axons descend in ventral white column of spinal cord • Axons terminate in ipsilateral ventral horn cells of spinal cord

RETICULOSPINAL TRACTS LATERAL RETICULOSPINAL TRACT • Cells of origin: medullary reticular formation • Axons descend in ventral white column of spinal cord on both sides (both crossed & uncrossed) • Axons terminate in ipsilateral & contralateral ventral horn cells of spinal cord

RETICULOSPINAL TRACTS • Concerned with control of reflex activity & muscle tone