Parallel fiber

Parallel fiber
Microcircuitry of the cerebellum. Excitatory synapses are denoted by (+) and inhibitory synapses by (-). MF: Mossy fiber. DCN: Deep cerebellar nuclei. IO: Inferior olive. CF: Climbing fiber. GC: Granule cell. PF: Parallel fiber. PC: Purkinje cell. GgC: Golgi cell. SC: Stellate cell. BC: Basket cell.
Details
Latin	Fibra parallela
Dorlands /Elsevier	f_05/12361338
Anatomical terminology []

Parallel fibers arise from granule cells in the cerebellar cortex. They form excitatory synapses onto the dendrites of Purkinje cells (the output neurons of the cerebellum) and the dendrites of the inhibitory interneurons basket cells and stellate cells of the molecular layer.

Granule cells are very small and very numerous. They are thought to make up as many as half of the neurons in the brain. Granule cells have axons which rise up and then branch out into parallel fibers. These fibers intersect the Purkinje cell dendrites.