Abstract: The nervous system in all vertebrates is composed of neurons, glial cells, and ependymal cells. The latter line the ventricular surfaces, while the glia are interspersed with neurons. Neurons are the active, conductive elements of the nervous system. For all spinal nerves and most cranial nerves, the sensory, bipolar neuron cell bodies lie within peripherally located ganglia and project to multipolar neurons within the central nervous system. The multipolar neurons that receive input from the sensory bipolar neurons are the first in a chain of several multipolar neurons that relay the sensory information rostrally along the neuraxis and can thus be referred to as first-order multipolar neurons. In most cases, the first order multipolar neurons project rostrally to one of two sites: either to a nucleus within the diencephalon or to part of the midbrain roof. In the latter case, the midbrain roof then projects rostrally to a nucleus within the diencephalon. Diencephalic cell groups subsequently project to the telencephalon. A number of telencephalic regions receive these various sensory inputs and are extensively interconnected with each other. The basic templates for motor pathways follow a similar multi-synaptic strategy. Various sites within the telencephalon project either to the midbrain roof directly or to diencephalic nuclei, which in turn project to more caudal levels, including the midbrain roof. The latter structure and numerous other sites relay descending motor information to the reticular formation in the brainstem, which in anamniotes is the major source of descending projections to the motor nuclei of cranial nerves and to motor neurons within the spinal cord.
Publication Year: 2000
Publication Date: 2000-01-01
Language: en
Type: book-chapter
Indexed In: ['crossref']
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Cited By Count: 23
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