The human brain is primarily composed of neurons , glial cells , neural stem cells , and blood vessels . Types of neuron include interneurons , pyramidal cells including Betz cells , motor neurons ( upper and lower motor neurons ), and cerebellar Purkinje cells . Betz cells are the largest cells (by size of cell body) in the nervous system.  The adult human brain is estimated to contain 86±8 billion neurons, with a roughly equal number (85±10 billion) of non-neuronal cells.  Out of these neurons, 16 billion (19%) are located in the cerebral cortex, and 69 billion (80%) are in the cerebellum.