Formation of Dendrites and Development of Synaptic Connections
Five cardinal theories of the organization of nervous systems originated in the second half of the 19th century and formed the basis of the neuron theory on which modem neuroscience research programs are constructed. The most important advance in our understanding of the historical development of the neuron theory is that it did not originate in the 1880s and 1890s as a single theory but was constructed over a much longer period, starting in the 1840s, by convergence of at least five different cardinal theories and several other auxiliary theories. Those cardinal theories were, firstly, that the nerve cell and its fibers are parts of the same unit (Wagner, 1847; Koelliker, 1850; Remak, 1853, 1855); secondly, that nerve fibers are protoplasmic outgrowths of nerve cells (Bidder and Kupffer, 1857; His, 1886); thirdly, that dendrites and axons are fundamentally different types of nerve fibers (Wagner, 1851; Remak, 1854; Deiters, 1865; Golgi, 1873, 1882-1885); fourthly, that nerve conduction occurs in only one directionfrom dendrites to axons in the same nerve cell, and from axons to dendrites between different nerve cells (van Gehuchten, 1891; Lenhossek, 1893; Ramon y Cajal, 1895); fifthly, that nerve cells are connected by surface contact and not by cytoplasmic continuity (Koelliker, 1879, 1883, 1886; His, 1886; Forel, 1887).
KeywordsMigration Cobalt Norepinephrine Choline Catecholamine
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