Self Comes to Mind

internal (mesial) surface. Two regions of the cerebral cortex that are not visible at all when one inspects the surface of the cerebellum are the insular cortex , buried underneath the frontal and parietal regions; and the hippocampus , a special cortical structure hidden in the temporal lobe.
    Underneath the cerebral cortex, the central nervous system also includes deep conglomerates of nuclei such as the basal ganglia , the basal forebrain , the amygdala , and the diencephalon (a combination of the thalamus and the hypothalamus) . The cerebrum is joined to the spinal cord by the brain stem , behind which the cerebellum is located with its two hemispheres. Although the hypothalamus is usually mentioned together with the thalamus to constitute the diencephalon, in reality the hypothalamus is functionally closer to the brain stem, with which it shares the most critical aspects of life regulation.
    The central nervous system is connected to every point of the body by bundles of axons originating in neurons. (The bundles are known as nerves.) The sum total of all nerves connecting the central nervous system with the periphery and vice versa constitutes the peripheral nervous system . Nerves transmit impulses from brain to body and from body to brain. One of the oldest and most important sectors of the peripheral nervous system is the autonomic nervous system , so called because its operation is largely outside our volitional control. The components of the autonomic nervous system include the sympathetic, parasympathetic , and enteric systems. The system plays a critical role in life regulation and in emotions and feelings. The brain and the body are also interconnected by chemical molecules such as hormones, which travel in the bloodstream. The ones that travel from brain to body originate in nuclei such as those in the hypothalamus. But chemical molecules also travel in the opposite direction and influence neurons directly at locations such as the area postrema, where the protective blood-brain barrier is missing.

     
Figure A.1 : The large-scale architecture of the human brain shown in a three-dimensional reconstruction of magnetic resonance data. The lateral (external) views of both right and left cerebral hemispheres are shown on the left panels; the medial (internal) views are shown on the right. The white curved structure in the right panels corresponds to the corpus callosum.

     
Figure A.2: The panels on the left depict three-dimensional reconstructions of the human brain seen from lateral and medial perspectives (top and bottom, respectively).
The panels on the right depict three sections of the brain volume. The sections were obtained along the lines marked a, b , and c . The sections reveal a number of important brain structures located under the surface: 1 = basal ganglia; 2 = basal forebrain; 3 = claustrum; 4 = insular cortex; 5 = hypothalamus; 6 = thalamus; 7 = amygdala; 8 = hippocampus. The cerebral cortex covers the entire surface of the cerebral hemispheres, including the depth of every sulcus. In the sections, the cerebral cortex appears as a dark rim easily distinguishable from the lighter white matter underneath. The black areas at the center of the sections correspond to the lateral ventricles.
    (The blood-brain barrier is a protective shield against certain molecules circulating in the bloodstream.) The area postrema is located in the brain stem, very close to important life-regulating structures such as the parabrachial and periaqueductal nuclei.
    When one slices the central nervous system in any direction and looks at the cross-section, one notices a difference between dark and pale sectors. The dark sectors are known as the gray matter (although they are more brown than gray), and the pale sectors are known as the white matter (which is more tan than white). The gray matter gets its darker hue from the tight packing of many neuron cell bodies; the white matter gets its lighter appearance from the insulating sheaths of the axons that emanate from the cell bodies located in the gray matter. As noted, the insulation is made of myelin and speeds up the conduction of electric current in the axons. Myelin insulation and fast conduction of signals are hallmarks of evolutionarily modern axons. Unmyelinated fibers are quite slow and of older vintage.
    The gray matter comes in two varieties. By and large the layered variety is found in the cerebral cortex , which envelops the cerebral hemispheres, and