In addition, they receive strong excitatory signals from the vestibular nuclei, as well as from deep nuclei of the cerebellum. The pontine reticular nuclei have a high degree of natural excitability. The fibers of this pathway terminate on the medial anterior motor neurons that excite the axial muscles of the body, which support the body against gravityâ€”that is, the muscles of the vertebral column and the extensor muscles of the limbs. The pontine reticular nucleitransmit excitatory signals downward into the cord through the pontine reticulospinal tract in the anterior column of the cord, as shown in Figure 55â€“8.

These two sets of nuclei function mainly antagonistically to each other, with the pontine exciting the antigravity muscles and the medullary relaxing these same muscles. (1) pontine reticular nuclei, located slightly posteriorly and laterally in the pons and extending into the mes-encephalon, and (2) medullary reticular nuclei, which extend through the entire medulla, lying ventrally and medially near the midline. The reticular nuclei are divided into two major groups: Support of the Body Against Gravity- Roles of the Reticular and Vestibular Nucleiįigure 55â€“7 shows the locations of the reticular and vestibular nuclei in the brain stem.Įxcitatory-Inhibitory Antagonism Between Pontine and Medullary Reticular Nuclei

Support against gravity circuit