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 contralateralventral 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 TRACTSLATERAL 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