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Purves D, Augustine GJ, Fitzpatrick D, et al., editors. Neuroscience. 2nd edition. Sunderland (MA): Sinauer Associates; 2001.

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Neuroscience. 2nd edition.

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The Midline Sagittal Surface of the Brain

When the brain is hemisected in the midsagittal plane, all of its major subdivisions plus a number of additional structures are visible on the cut surface (Figure 1.14). In this view, the cerebral hemispheres, because of their great size, are still the most obvious structures. The frontal lobe of each hemisphere extends forward from the central sulcus, the medial end of which can just be seen (Figure 1.14A,B). The parieto-occipital sulcus, running from the superior to the inferior aspect of the hemisphere, separates the parietal and occipital lobes. The calcarine sulcus divides the medial surface of the occipital lobe, running at very nearly a right angle from the parieto-occipital sulcus and marking the location of the primary visual cortex. A long, roughly horizontal sulcus, the cingulate sulcus, extends across the medial surface of the frontal and parietal lobes. The prominent gyrus below it, the cingulate gyrus, along with the cortex adjacent to it, is sometimes called the “limbic lobe” (the use of the term lobe here is used only loosely, as this region is not considered a fifth lobe of the brain). The”limbic lobe” (limbic means border or edge), which wraps around the corpus callosum, and the subcortical areas connected to it are referred to as the limbic system. These limbic structures are important in the regulation of visceral motor activity and emotional expression, among other functions. Finally, ventral to the cingulate gyrus is the midsagittal surface of the corpus callosum.

Figure 1.14. Midsagittal view of the human brain.

Figure 1.14

Midsagittal view of the human brain. (A) Major features apparent after bisecting the brain in this plane. (B) The lobes of the brain seen from its medial surface. (C) An enlarged view of the diencephalon and brainstem in this view.

Although parts of the diencephalon, brainstem, and cerebellum are visible at the ventral surface of the brain, their overall structure is especially clear from the midsagittal surface (see Figure 1.14A). From this perspective, the diencephalon can be seen to consist of two parts. The dorsal thalamus, the largest component of the diencephalon, comprises a number of subdivisions, all of which relay information to the cerebral cortex from other parts of the brain. The hypothalamus, a small but especially crucial part of the diencephalon, is devoted to the control of homeostatic and reproductive functions. The hypothalamus is intimately related, both structurally and functionally, to the pituitary gland, a critical endocrine organ whose posterior part is attached to the hypothalamus by the pituitary stalk (or infundibulum; Figure 1.14C).

The midbrain, which can be seen only in this view, lies caudal to the thalamus, with the superior and inferior colliculi defining its dorsal surface or tectum (meaning “roof”); several midbrain nuclei, including the substantia nigra, lie in the ventral portion or tegmentum (meaning “covering”) of the midbrain. The other prominent anatomical feature of the midbrain—the cerebral peduncles (also visible from the ventral surface)—are not apparent in a midsagittal view. The pons is caudal to the midbrain along the midsagittal surface, and the cerebellum lies over the pons just beneath the occipital lobe of the cerebral hemispheres. The major function of the cerebellum is coordination of motor activity, posture, and equilibrium. From the midsagittal surface, the most visible feature of the cerebellum is the cerebellar cortex, a continuous layered sheet of cells folded into ridges and valleys called folia. The most caudal structure seen from the midsagittal surface of the brain is the medulla, which merges into the spinal cord.

By agreement with the publisher, this book is accessible by the search feature, but cannot be browsed.

Copyright © 2001, Sinauer Associates, Inc.
Bookshelf ID: NBK10798

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