ABSTRACT
The cerebellar cortex has three layers and contains five cell types that are organized into a simple circuit repeated millions of times. The major input to the cerebellum are mossy fibers, axons of second order neurons from the spinal cord and brainstem conveying proprioceptor input, or the pontine-cerebellar relay from the cerebral cortex conveying sensory and motor signals. Mossy fibers are glutamatergic and excitatory, and after giving off an axon collateral which goes to the appropriate deep cerebellar nucleus, they synapse with granule cells in synaptic complexes called glomeruli. The sole output of the cerebellar cortex is via the Purkinje cells which have their large cell bodies in the Purkinje cell layer of the cortex. Their extensive dendrites are aligned into a flat plane and are all oriented in the same direction, at right angles to the long axis of the folium in which they are located.
