Lab 9 - Descending Pathways to the Spinal Cord

Vestibulospinal Pathways - Spinal Cord

The figures are transverse sections through the spinal cord starting at the cervical cord. View and identify the structures in the illustration.

Layer A is through the sacral cord. Within the anterior funiculus only the lateral vestibulospinal tract and the pontine and medullary reticulospinal tracts are present. The lateral vestibulospinal tract fibers facilitate reflex activity and control tone in extensor leg and foot muscles.

Layer B is through the lumbar cord. The posterior spinocerebellar tract is barely developed and the lateral corticospinal tract is located near the posterolateral margin of the lateral funiculus. The rubrospinal tract, which is located in the lateral funiculus, is smaller at this point. The tectospinal and medial vestibulospinal tracts are both in the anterior funiculus. Within the anterior funiculus are the anterior corticospinal tract (much reduced in size here), pontine and medullary reticulospinal tracts and lateral vestibulospinal tract.

Layer C is through the thoracic cord. Few fibers of the medial vestibulospinal tract and none of the tectospinal tract extend beyond thoracic levels of the human spinal cord. The descending tracts in the anterior funiculus include the lateral vestibulospinal tract, the pontine and medullary reticulospinal tracts and the anterior corticospinal tract.

Layer D is through the cervical cord. The medial and lateral vestibulospinal, reticulospinal and tectospinal tracts are located in the anterior funiculus of the spinal cord. The medial vestibulospinal tract fibers terminate bilaterally at cervical and mid-thoracic levels while the majority of the lateral vestibulospinal tract fibers terminate ipsilaterally at all spinal cord levels. These fibers terminate on neurons, which exert a facilitatory influence on reflex activity and control muscle tone of the antigravity (extensor) muscles.