SOMATIC MOTOR NEURONS 3 DESCENDING pathways, adjusted by basal nuclei & cerebellum:

COTRICOSPINAL PATHWAY conscious & voluntary, 3 tracts:

LATERAL PATHWAY extrapyramidal, subconscious & reflexes; modify skel muscles by

stimulating or inhibiting LMN; 1 tract:

MEDIAL PATHWAY extrapyramidal, subconscious & reflexes;

modify skel muscles by stimulating or inhibiting LMN; 3 tracts:

CORTICOBULBAR -from UMN [pyramid cells] in prim sens cortex/ precentral gyri -axons down brainstem -synapse with LMN in nuclei of 9 CN [not 1, 2, 8] -output to effectors: eye, face, jaw, neck

LATERAL CORTICOSPINAL

-from UMN [pyramid cells] in prim sens cortex/ precentral gyri -axons down brainstem as pyramids -cross over to opposite sides in medulla -down through lateral column of SC -synapse with LMN in ventral horn -output to effectors: limbs

ANTERIOR COTRICOSPINAL

-from UMN [pyramid cells] in prim sens cortex/ precentral gyri -axons down brainstem as pyramids -down through anterior/ventral column of SC -synapse with LMN in ventral horn -output to effectors: axial skeleton muscles—trunk, thoracic cage, vertebral column

VESTIBULOSPINAL -from UMN in vestib nuclei in CN 8 of brainstem & inner ear receptors -axons down brainstem to SC -down through anterior/ventral column -synapse with LMN in ventral horn -monitors head movmt & position -output to effectors: reflex muscles of EHNT [eye, head, neck, trunk]—maintain balance & muscle tone

TECTOSPINAL -from UMN in tectal plate of corpora quadrigemina [sup

& inf colliculi] in mesencephalon -axons down brainstem -cross over to opposite sides in medulla -down through anterior/ventral column of SC -synapse with LMN in brain OR ventral horn -output to effectors: reflex muscles of EHNT -reflexes for aud & visual stimuli

RETICULOSPINAL -from UMN in reticular form [interconnected with cerebrum & brainstem & input from all pathways] -axons down brainstem -down through anterior/ventral column of SC -synapse with LMN in ventral horn -output to effectors is VARIED: increase eye mvmt & resp muscle activity when awake

RUBROSPINAL -from UMN in red nuclei of mesencephalon [receives input from cerebral cortex & cerebellum] -axons down brainstem -cross over to opposite sides in medulla -down through lateral column of SC -synapse with LMN in ventral horn -output to effectors: cervical spinal muscles for precise mvmt of distal upper limbs