The spinal cord descends from the brainstem down through the shielded tunnel of the vertebrae,  and transmits information from the body to the brain and from the brain to the body. Thus, the central nervous system is composed of nerves the are rooted to both the surface of the brain, as well as to the spinal cord. Most nerves are peripheral nerves, which extend and branch toward the surface of the body.<br><br><p style="text-align: center;"><img src="@@PLUGINFILE@@/spinal-cord.png" alt="Spinal Cord" width="438" height="275" class="img-responsive atto_image_button_text-bottom" style="font-size: 1rem;"></p><p style="text-align: center;"><br></p><p style="text-align: left;">The brain grows like an onion. The triune brain was first described by MacLean in 1990, as consisting of three layers that depict our evolution individually as a species. The first layer is the reptilian brain (its core), responsible for activation, arousal, homeostasis, and reproductive drives. This is the dinosaur brain, the same brain that has been around for 2,000,000 years. The reticular formation at the conjunction of the thalamus and the brainstem oscillates at 2 Hz (delta) (Thatcher, 2015). At birth, this structure is already in place and fully functional.&nbsp;<br></p>