Anatomy and Physiology: The Control Center

The Control Center

One of the amazing things about the brain is the idea of neuronal plasticity. Neurons have the ability to adapt and adjust to different sensory input, often within minutes. This explains how blind people have such well-developed hearing and sense of touch: Unused neurons are used to process sensory input from the other senses. This becomes important as you look at the specific areas of the brain. Many people want to know which parts of the brain are used for what functions.

Although we have a general idea, things are actually more complicated than they look on the surface. On a cellular level, apart from a fissure here and a sulcus there, few regions of the brain are clearly anatomically distinguishable. Functions can extend into neighboring areas, not to mention areas carrying out multiple functions. We might be able to specify, at least to a certain extent, the speech area, but what about consciousness, which appears to involve gray matter all over both hemispheres?

Dem Lobes, Dem Lobes, Dem Four Lobes

Now I told you those cranial bones would come in handy, because the four lobes of the cerebrum can all be found directly under the cranial bones of the same name (see Figure 20.5). These lobes are separated by various sulci, such as the central sulcus separating the frontal and parietal lobes. Each of these lobes is, however, continuous with the others when you look at the white matter deeper within.

Figure 20.5

The four lobes of the brain, and several important areas of specialization. (LifeART©1989-2001, Lippincott Williams & Wilkins)

The division is really somewhat arbitrary, even, to a certain extent functionally, because the functions that appear to be on the border of one lobe may very well have active neurons in the neighboring lobe. Some functions are so obviously distant from other lobes that they can be considered unique to that lobe, and yet others, such as consciousness really involve multiple lobes. With that in mind, the following table indicates the areas of each lobe, and the functions associated with them.

Cerebellum

The pair of cerebellar lobes, which extend out the back of the pons (see the brainstem), around the fourth ventricle, is pretty cool. Similar to the cerebrum, there are two cerebellar hemispheres that are each divided into an anterior lobe and a posterior (middle) lobe, plus a lobe involved with balance hidden underneath, that has the coolest name: flocculonodular lobe.

Yeah, yeah, but what does it do? Well, it turns out that the primary motor cortex doesn't really do the greatest of jobs! When instructions are sent from the frontal cortex, the cerebellum coordinates the movement to make it smooth. With very complex movements, such as playing an instrument, the cerebellum is essential! Walking would not be possible if it weren't for the coordination of the muscles, and the detected balance, in the cerebellum.

Excerpted from The Complete Idiot's Guide to Anatomy and Physiology © 2004 by Michael J. Vieira Lazaroff. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books, a member of Penguin Group (USA) Inc.

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