Axons anatomy

Tire anatomy of the brain is quite complex, and only a few terms will be defined here. Tire cerebrum, which is made up of two hemispheres, accounts for the largest part of the brain. Tire deeply folded outermost layer, the cerebral cortex, consists of gray matter, a mass of cell bodies, and fine unmyelinated nerve fibers. Beneath this lies a layer of white matter made up of myelin-covered axons connecting the cerebral cortex with other parts of the brain. Tire two cerebral hemispheres are connected by the corpus callosum, a band of 2 x 108 nerve fibers. Remarkably, these fibers can be completely severed with a relatively minimal disruption of the nervous system. In the past the corpus callosum was sometimes cut to control almost incessant epileptic seizures that could not be prevented by drugs. The "split-brain" patients suffered relatively little disability as long as both eyes functioned normally. Studies of these patients provided some insights into the differing functions of the two hemispheres of the cerebrum.395... 

Reier PJ (1986) Gliosis following CNS injury The anatomy of astrocytic scars and their influences on axonal elongation. Astrocytes 3 263-324. 

In a recent review article on the anatomy of autism Amaral et al. (2008) point out that in these studies by Casanova and his colleagues, only 14 cases of autism, 9 of which had seizures and at least 10 with mental retardation, have been examined for minicolumn pathology. Consequently, more studies using a greater number of autistic brains with fewer other complications need to be carried out before any definite conclusions can be reached about changes that can only be attributed to autism. It would also be appropriate to examine brains in which the apical dendritic clusters and myelinated axon bundles have been stained to confirm the sizes of the minicolumns as detected in digitized images from autistic brains. 

Sotelo C, Gotow T, Wassef M (1986) Localization of glutamic-acid-decarboxylase-immunoreactive axon terminals in the inferior olive of the rat, with special emphasis on anatomieal relations between GABAergic synapses and dendrodendritic gap junctions. J. Comp. Neurol, 252, 32-50. 

The antidiuretic mechanism in mammals involves two anatomical components a CNS component for the synthesis, transport, storage, and release of vasopressin, and a renal collecting-duct system composed of epithelial cells that respond to vasopressin by increasing their permeability to water. The CNS component of this mechanism, called the hypothalamiconeurohypophyseal system, consists of neurosecretory neurons with perikarya located predominantly in two specific hypothalamic nuclei, the supraoptic nucleus (SON) and the paraventricular nucleus (PVN). The long axons of magnocellular neurons in the SON and PVN terminate in the neural lobe of the posterior pituitary (neurohypophysis), where they release vasopressin and oxytocin. The relevant anatomy of the renal collecting-duct system is described in Chapter 28. 

Many studies have focused on the anatomy and physiology of the cochlear nucleus (CN) revealing a wealth of information. It can be subdivided into three regions, the anteroventral CN (AVCN) anterior to the nerve entry, the posteroventral CN (PVCN), and the dorsal CN (DCN), each with one or more distinctive neuron types and connections. The axon from each Type I SGC in the nerve branches to each of the three divisions in an orderly manner so that tonotopic organization is maintained. Neurons with... 

Figure 6.1 Anatomy of a nerve. Nerves consist of a modal structure, comprised of an axon that is surrounded by a membrane called the endoneurium. Several of these axons comprise a fascicle, which is bounded by the perineurium. In turn, nmnetous fascicles make up the peripheral nerve, which is covered by the epineurium. The inset on the left shows an unmyelinated axon and the inset on the bottom shows a myelinated axon (Lee and Wolfe, 2000). Reproduced with permission from Elsevier Lundborg, G., 1987. Nerve regeneration and repair. A review. Acta Orthop. Scand. 58, 145-169.

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