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caudal__________THE DECUSSATION _________rostral

If you have been counting carefully, you realize that the medial pathway, as it descends into the spinal cord, actually includes 5 tracts: the tectospinal tract, two reticulospinal tracts (one originating in the pontine reticular formation, the other in the medullary reticular formation) and two vestibulospinal tracts (medial and lateral). They do different things but are lumped together because they pass down through the medial part of the brainstem. While there are exceptions, it is reasonably accurate to say that they all descend in the anterior funiculus of the spinal cord and that they exert their greatest influence on "lower motor neuron" innervating axial and trunk muscles. Thus they act, by way of interneurons, on motor neurons in the medial part of the anterior horn. The anatomy of these tracts has been worked out in detail, and most textbooks tell you exactly where each tract is to be found in the spinal cord. We don't think you need to know that much detail, so in this figure we lump all of them together and represent them by the green hatchmarks. Blumenfeld's Figure 6.7 is similar. Our one exception is to show the tectospinal tract (light blue) separately. Click on "key" to look at the next (rostral or caudal) slide. Click on the red ball to return to the text, by way of the call-up view)