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Descending tracts of spinal cord

Tract

Situation

Origin

Course

Function

Pyramidal tracts

1. Anterior corticospinal

tract

Anterior white funiculus

Betz cells

and other

cells of

motor area

Uncrossed

fibers

1. Control of voluntary

movements.

2. Upper motor

Neurons functions

2. Lateral corticospinal

tract

Lateral white funiculus

Betz cells

and other

cells of

motor area

Crossed

fibers

Extra-pyramidal tracts

1. Medial longitudinal fasciculus

Anterior white fasciculus

Vestibular

nucleus.

Reticular

formation.

Superior

colliculus and

cells of Cajal

Uncrossed

fibers.

Extend up

to upper

cervical

segments

1. Coordination of

reflex ocular move-

ments.

2. Integration of

movements of eyes

and neck.

2. Anterior vestibulo-

spinal tract

Anterior white funiculus

Medial

vestibular

nucleus

Uncrossed

fibers.

Extend up

to upper

thoracic

segments

1. Maintenance of

muscle tone and

posture.

2. Maintenance of

position of head

and body during

acceleration

3. Lateral vestibule-

spinal tract

Lateral white funiculus

Lateral

vestibular

nucleus

Mostly un-

crossed.

Extend to

all segments

4. Reticulo-

spinal tract

Lateral white fasciculus

Reticular

formation

of pons

and medulla

Mostly un-

crossed.

Extend upto

thoracic

segments

1. Coordination of

voluntary and reflex

movements.

2. Control of muscle

tone.

3. Control of respi-

ration and blood vessels

5. Tectospi-

nal tract

Anterior white funiculus

Superior

colliculus

Crossed fibers.

Extend up to

lower cervical

segments.

Control of movement

of head in response to

visual and auditory

impulses

6. Rubro-

spinal tract

Lateral white funiculus

Red nucleus

Crossed fibers.

Extend up to

thoracic seg-

ments.

Facilitatory influence

on flexor muscle tone

7. Olivo-

spinal tract

Lateral white funiculus

Inferior

olivary

nucleus

Mostly crossed.

Extent—not clear.

Control of movements

due to proprioception

Termination — Fibers of all the tracts terminate in motor neurons situated in the anterior gray horn of spinal cord

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