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Understanding the Corticospinal Pathways in Neuroanatomy

Learn about the structure and function of corticospinal tracts, pathways, and their different components, such as the lateral and ventral tracts. Explore how these pathways influence voluntary movements and motor activity.

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Understanding the Corticospinal Pathways in Neuroanatomy

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  1. DESCENDING TRACTS Dr. Ahmed Fathalla Ibrahim

  2. 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)

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

  4. 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

  5. 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 contralateralventral horn cells of spinal cord

  6. CORTICOSPINAL TRACTS

  7. 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

  8. 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

  9. RUBROSPINAL TRACTS

  10. 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

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

  12. 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 ipsilateralventral 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

  13. 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

  14. 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

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

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