Decussations and terminations of the descending tracts (fall 2023, exam 2)

Could terminate anywhere from dorsal horn to intermediate zone or lamina VIII to the motoneurons themselves. Any single cell will have a focused termination in a particular part of the spinal gray, any level of the cord

Lateral corticospinal

Decussation of the pyramids at the lowest part of medulla right before it turns into spinal cord

Lateral corticospinal tract

Terminations to the lateral part of grey matter for interneurons to affect motoneurons, just a few segments at a time can be in cervical, lumbar or thoracic

Lateral reticulospinal tract

This tract also does not decussate

Lateral reticulospinal tract

Terminations in lamina vII, VIII, IX to excite antigracity muscle ipsilaterally mono and/or disynaptic connections to motor pools

Lateral vestibulospinal

This tract does not decussate

Lateral vestibulospinal

Decussate at the spinal cord level where the axon terminates, some braches cross to the other side while some terminate ipsilaterally

Medial reticulospinal

Terminates in ventromedial or lateral part of ventral horn. Monosynaptic possible but more often through interneurons to motoneurons. Can be on either side, single cells can give off branches at multiple levels ranging from cervical through thoracic and lumbar segments from one reticulospinal cell

Medial reticulospinal

Contralateral branches decussate immediately as soon as the axon comes out of the medial vestibular nucleus in the lower pons/upper medulla

Medial vestibulospinal

Termination is a lot like tectospinal, the difference being that it can be ipsilateral or contralateral, and what drives the activity. Terminations similar to tectospinal being interneurons one synapse away from motorneurons in the ventral gray matter in

Medial vestibulospinal tract

Terminations in lamina VII and some in lamina IX in lateral/ventral horn of cervical region

Rubrospinal

Decussates immediately in the midbrain as soon as the axon comes out of the red nucleus

Rubrospinal tract

Decussates immediately in the midbrain as soon as the axon comes out of the superior colliculus

Tectospinal

Terminations are interneurons on synapse away from motoneurons in the ventral gray matter in cervical cord

Tectospinal tract

Some axon branches may decussate at the spinal segmental level right where they termiante

Ventral corticospinal tract

Terminations in cervical and upper thoracic little to no lumbar, mostly medial in the spinal gray, lamina III probably disynaptic not monosynaptic to motor pools, sometime bilateral through collateral branches

Ventral corticospinal tract