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CROSS SECTION OF A CEREBELLAR FOLD is diagrammed to show the network of cells which transmits nerve impulses though it. Nerve impulses enter the fold though the white matter (broken lines in center). These impulses are drawn into the cortex, or grey matter, by the granule cells (a). Each granule receives an impulse through its short dendrites. It transmits the impulse into the outer, or "molecular," layer of the fold though its long, T-shaped axon. In the molecular layer the impulse passes from these axons into the many-branched dendrites of the Purkinje cells (b). The impulse then leaves the cerebellar fold through the axon of the Purkinje cell, embedded in the white matter at the center. The process by which impulses pass from the granule cells to Purkinje cells is abetted by basket cells (c). Each basket cell picks impulses from a granule-cell axon, then transmits them through a long fiber to "baskets" of fibrils which surround the cell bodies of several Purkinje cells. Other auxiliary cells are the "mossy terminals" (d) and Golgi Type-II cells (e) which help diffuse incoming and outgoing impulses respectively. Cell-types f and g are of unknown function; h is a climbing fiber whose axon adheres to the Purkinje cell dendrites and may serve to "switch" them on and off. (Reprinted from Scientific American, Aug 1958)
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