What are parallel fibers?
parallel fibers are myelinated axonal projections that range from granular cells in the cerebellar cortex. Granul cell axons grow towards the burkinjový cells in the molecular layer of the cerebellar, which is a place where arborization dendritic fields of burkinj cells are arborized. Purkinje cells are the outlet cells of the brain. Thousands of synapses created between parallel fibers made of granules and dendritic arborization of burkinjový cells are excitation and use glutamate as a neurotransmitter. Although this area forms a relatively small part of the volume of the whole brain, it is assumed that the cells of granules found in the brain include about half of the cells in the brain. These small cells, a diameter of about 10 microns in diameter, are found in other areas of the brain, but are the most numerous in the brain. Granules of the cell from which the parallel fiber project receive information from Mossvlákna, which are projections from cells found in pontin cores.
As indicated by the name of these fibers, the parallel fibers run perpendicular to the long axes of the dendritic field of the purkinj cells and in parallel to the surface of the cortex. The extension of projections from granules cells first rises before branching in parallel orientation to dendritic fields of burkinj cells. This is a unique characteristic, because for most neurons in the brain, the orientation of the main axis of the neurite, with apical dendrites and contradictory axon, perpendicular to the nearest cortical surface. Since there are so many sulci and cracks on the bark of the mammalus, many cells will change the orientation based on which cortical form is most close. For example, on one side of the crack, the layer of four pyramidal cell will lie sideways due to the pyramidal cell at the top of the sulcus.
Long -term depression occurs when parallel fibers are repeatedly activated simultaneously, which has a direct effect on the function of these cells, especially because they are innervated by inhibitory moschGolgi, which pushes the circuit towards the default synchronous shooting pattern. The fact that it is possible to induce long -term depression suggests that these fibers or granular cells from which they extend can change their shooting properties based on previously received and transmitted information. In other words, these cells can "learn" at a slight autonomous level.