Page Comparison - Santiago Ramón y Cajal Exhibit (v.102 vs v.103)

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In 1905, Cajal studied human sympathetic ganglia and found morphological arrangements he had not yet seen in other species. Sympathetic ganglia comprises the thousands of afferent and efferent nerve cell bodies that run along either side of the spinal cord, connecting major organ systems, such as the renal system, to the spinal cord and brain. The kidney, a main organ within the renal system, filters blood to remove toxins via millions of structures called glomeruli, consisting of a tuft of blood vessels surrounded by a cuplike cellular structure known as Bowman’s Capsule. Shown above is a single neuron innervating a single glomerulus from a 50-year-old human subject, with a distinctive “comet” shape comprised of a very rich periglomerular nerve arborization. The kidney is innervated by both sympathetic and parasympathetic fibers; the innervating parasympathetic fibers originate from the vagal nerve. Pain signals caused by kidney stones may activate cross signaling along the vagal route, causing the well-known nausea and vomiting associated with kidney stones via the pathway shown in drawing no. 5.

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Courtesy of the Cajal Institute, Spanish National Research Council or CSIC^©

Development of climbing fibers (afferents) on Purkinje cells of the cerebellum.

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During cerebellar development, climbing fibers reach the Purkinje cell bodies, making perisomatic contacts. Later they reach the dendrites and the contacts they make with these cells are perisomatic and peridendritic and, at the end of their development, the contacts are reduced to exclusively peridendritic.

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Courtesy of the Cajal Institute, Spanish National Research Council or CSIC^©

Elements of the plexiform cortical layer (layer 1). Cajal–Retzius cells.

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In 1890, Cajal published a paper (Sobre la existencia de células nerviosas especiales en la primera capa de las circunvoluciones cerebrales. Gaceta médica catalana, nº 23: 737-739) reporting the existence of special nerve cells in the first layer of the cerebral cortex of lower mammals. He called them special because they had a unique peculiarity: they had two or more axons. Soon after, Gustav Retzius described the same cells in higher mammals and primates. Since then, they have been known as Cajal-Retzius cells. Today it is known that they are the first cell population to appear in the developing cerebral cortex and their importance in the stratification of this structure, through the secretion of the reelin protein.

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Courtesy of the Cajal Institute, Spanish National Research Council or CSIC^©

Neurons of the optic tectum of birds (Theory of Axipetal Polarization).

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In 1891, Cajal enunciated his Law of Dynamic Polarization at a Medical Congress in the city of Valencia. This Law says that the nervous impulse is polarized, going in only one direction. This is so, he explained, because the neuron receives the nerve impulse in its dendrites, transports it to the cell body and releases it through the terminal buttons of its axon, which come into contact with the dendrites of other cells. However, studying the optic tectum of birds in 1892, he found neurons whose axon does not emerge from the cell body, but from one of its dendrites, so his theory of Dynamic Polarization could not be fulfilled. He studies this phenomenon and realizes that, in these cases, the nerve impulse did not need to reach the cell body and have to go back through the dendrite to be able to exit through the axon, but was released directly through the axon without having to first reach the cell body. He then formulates a variation to his theory of Dynamic Polarization, which he enunciates as Theory of Axipetal Polarization.

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Courtesy of the Cajal Institute, Spanish National Research Council or CSIC^©

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6th Installation (current)

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Versions Compared

Old Version 102

New Version 103

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Development of climbing fibers (afferents) on Purkinje cells of the cerebellum.

Elements of the plexiform cortical layer (layer 1). Cajal–Retzius cells.

Neurons of the optic tectum of birds (Theory of Axipetal Polarization).

6th Installation (current)

Office of NIH History and Stetten Museum