nsists primarily of nerve cell bodies and unmyelinated nerve fibers. In contrast, deeper within the cerebrum, the whiter tissue is mainly composed of myelinated axons (Psychology text, p. 48).
Evolutionary advances among the mammals have generally resulted in increased development of the cerebral cortex. For example, the cortex of lower mammals tends to be small and fairly smooth. However, in humans, there is not only increased cerebral cortex relative to total brain tissue, the cortex tissues are also considerably more convoluted. These wrinkles ultimately result in a far greater surface area than occurs with a smooth cerebrum (Psychology text, p. 50).
Overall, the human brain may be divided into two nearly symmetrical hemispheres. Furthermore, each of these two hemispheres additionally consists of four distinct lobes. For example, running from the top of the head laterally and caudally, each hemisphere's central fissure separates its frontal lobe from its parietal lobe. Moreover, although the demarcation is less distinct, the occipital lobe lie
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