Figure 8. A. A view of the dorsal aspect of the embryo showing the location of the neural epithelium and the successive stages of closure of the neural tube. Note that the anterior and posterior neuropore are open at each end in the lower figure. B. The neural tube in the region that will be the spinal cord (left) and brain stem (right). Note how the alar plates have separated from one another in the view at the left. The motor cranial nerve nuclei are ventromedial to the sulcus limitans and the sensory nuclei are dorsolateral. GSE = general somatic efferent (somatic motor to eyes and tongue); GVE = general visceral efferent (parasympathetic); SVE = special visceral efferent (branchial motor to larynx, pharynx and jaw muscles); GVA = general visceral afferent (visceral sensory); GSA = general somatic afferent (somatic sensory); SSA = special somatic afferent (hearing and vestibular function). Special visceral affterent (SVA; taste fibers) terminate in nuclei in the same general region as GVA.