The Cerebellar Cortex The cerebellar cortex consists of three layers: the molecular layer, the granule cell layer and the Purkinje cell layer in the middle. The input to the cerebellum comes via the mossy fibers and via the climbing fibers. Both of these are glutamatergic. # The mossy fibers come from various sources including the pons and the spinal cord (medulla spinalis). The terminals of the mossy fibers are exceptionally large. They have multiple release sites that face granule cell dendrites. The granule cell dendrites also receive inhibitory input from Golgi cell terminals. Because the mossy fiber terminals are large (like a small cell body) are surrounded by multiple granule cell dendrites, it follows the the complexes of synapses is large and characteristic. The entire complex is often called a glomerolus. # The granule cells are the most abundant cell type in the CNS. There are more granule cells than all other CNS cells combined. These cells give rise to the parallel fib
