The cerebellum has two hemispheres and a folded cortical surface. It is attached to the brain stem where all the communication in and out of cerebellum goes through. The surface of the cerebellum is tightly folded which makes it look somewhat different compared to the cerebral cortex. The cerebellum is evolutionally the oldest part of the human brain, but is not specific for humans, and can be found in other species. One of its main functions is to control movement and coordination when receiving sensory input from the spinal cord and other regions of the central nervous system. However, it does not execute movements but it does finetune and coordinate movement and posture. When the cerebellum is damaged it can alter movement patterns and cause symptoms such as walking irregularities, force and speed defects and balancing.
The cerebellar cortex includes three layers:
The molecular layer, containing neurons, glial cells, neuropil and dendrites. The Purkinje layer, containing purkinje cells, purkinje dendrites and interneurons, and the granular layer which contains granule cells and synaptic glomeruli as well as blood vessels.
All three layers include a large number of specialized neurons, making the cerebellum the most neuronal dense region of the human brain. It is estimated to include 80% of all the neurons in the brain, but it only represents 10% of the brain volume.
Cerebellum is also rich in white matter that contains myelinated axons. These axons relay to grey matter structures such as neurons. White matter contains glial cells of different types such as oligodendrocytes, that produce myelin.
The meninges surrounding the brain tissue serves as a protective layer.