Diencephalon Sists of the Midbrain, Pons, and Medulla

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Diencephalon Sists of the Midbrain, Pons, and Medulla

Diencephalon The brain lies within the cranial cavity of the skull and is made up of billions of nerve cells (neu - rons) and supporting cells (glia) . Neuronal cell bodies group together as gray matter, and their processes group together as white matter. The brain can be divided into four main parts: the cerebrum, diencephalon, brain stem, and cere - bellum. • The cerebrum is the largest part of the brain and consists of the four paired lobes with the two cerebral hemispheres, connected by a mass of white matter called the corpus callosum. The cerebrum accounts for about 80% of the brain’s mass and is concerned with higher functions, including perception of sensory impulses, instigation of voluntary movement, memory, thought, and reasoning. There are two layers of the cerebrum: - The cerebral cortex is the thin, wrinkled gray matter covering each hemisphere - The cerebral medulla is a thicker core of white matter • The diencephalon lies beneath the cerebral hemispheres and has two main structures ¾ the thalamus and the hypothalamus. The walnut-sized thalamus is a large mass of gray matter that lies on either side of the third ventricle. The thalamus is a great relay station on the afferent sen - sory pathway to the cerebral cortex. The tiny hypothalamus forms the lower part of the lateral wall and floor of the third ventricle. The hypothalamus exerts an influence on a wide range of body functions. • The cerebellum is attached to the brain and features a highly folded surface. It is important in the control of movement and balance. • The brainstem is the lower extension of the brain where it connects to the spinal cord. It con - sists of the midbrain, pons, and medulla. Remember ¾ Each portion of the brain consists basically of three areas: 1. Gray matter ¾ composed primarily of unmyelinated nerve cell bodies 2. White matter ¾ composed basically of myelinated nerve fibers 3. Ventricles ¾ spaces filled with cerebrospinal fluid.

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Clones in the Chick Diencephalon Contain Multiple Cell Types and Siblings Are Widely Dispersed
Development 122, 65-78 (1996) 65 Printed in Great Britain © The Company of Biologists Limited 1996 DEV8292 Clones in the chick diencephalon contain multiple cell types and siblings are widely dispersed Jeffrey A. Golden1,2 and Constance L. Cepko1,3 1Department of Genetics, Harvard Medical School, 2Department of Pathology, Brigham and Women’s Hospital, and 3Howard Hughes Medical Institute, 200 Longwood Avenue, Boston, MA 02115, USA SUMMARY The thalamus, hypothalamus and epithalamus of the ver- clones dispersed in all directions, resulting in sibling cells tebrate central nervous system are derived from the populating multiple nuclei within the diencephalon. In embryonic diencephalon. These regions of the nervous addition, several distinctive patterns of dispersion were system function as major relays between the telencephalon observed. These included clones with siblings distributed and more caudal regions of the brain. Early in develop- bilaterally across the third ventricle, clones that originated ment, the diencephalon morphologically comprises distinct in the lateral ventricle, clones that crossed neuromeric units known as neuromeres or prosomeres. As development boundaries, and clones that crossed major boundaries of proceeds, multiple nuclei, the functional and anatomical the developing nervous system, such as the diencephalon units of the diencephalon, derive from the neuromeres. It and mesencephalon. These ﬁndings demonstrate that prog- was of interest to determine whether progenitors in the enitor cells in the diencephalon are multipotent and that diencephalon give rise to daughters that cross nuclear or their daughters can become widely dispersed. neuromeric boundaries. To this end, a highly complex retroviral library was used to infect diencephalic progeni- tors. Retrovirally marked clones were found to contain Key words: cell lineage, central nervous system, diencephalon, neurons, glia and occasionally radial glia.
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Thalamic Neuromodulation and Its Implications for Executive Networks
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Pt 311 Neuroscience
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