Lab 9 - Descending Pathways to the Spinal Cord

Reticulospinal Pathways - Spinal Cord

Figure 1 is a transverse section through the cervical cord. The descending tracts in the anterior funiculus include the lateral vestibulospinal tract, the pontine and medullary reticulospinal tracts and the anterior corticospinal tract.

Most of the pontine reticulospinal tract fibers remain uncrossed and terminate on neurons affecting axial and limb musculature. This tract extends the entire length of the spinal cord. These reticulospinal fibers facilitate voluntary and reflex responses and influence muscle tone. The bilateral, but mainly uncrossed, medullary reticulospinal tract fibers terminate on neurons at all levels of the spinal cord. The fibers have an inhibitory effect on voluntary and reflex responses of axial and limb muscles. Both the pontine and medullary reticulospinal tract fibers also influence respiration, sweating, vasomotor responses and other autonomic functions.

Figure 2 is a transverse section through the lumbar cord. The descending tracts in the anterior funiculus of the lumbar cord include the lateral vestibulospinal tract, the pontine and medullary reticulospinal tracts and a much reduced anterior corticospinal tract.

Figure 3 is a transverse section through the sacral cord. Within the anterior funiculus, the lateral vestibulospinal tract and the pontine and medullary reticulospinal tracts are present. The pontine reticulospinal tract fibers facilitate voluntary and reflex activity while the medullary reticulospinal tract fibers appear to inhibit both voluntary and reflex activity.