In the Central Nervous System, Human Brain is the main organ. It comprises of the cerebrum, the brain stem, and the cerebellum. It controls the vast majority of the body activities, processing, incorporating, and coordinating the data it gets from the sensory organs and deciding the instructions sent to rest of the body. The mind is contained in and secured by the skull bones of our head.

The human cerebrum is mainly made up of neurons, glial cells, and veins. Interneurons, pyramidal cells including Betz cells, motor neurons, and cerebellar Purkinje cells are the various types of neurons. Betz cells are the biggest cells in the sensory system. The grown-up human cerebrum is assessed to contain 86 ± 8 billion neurons and 85 ± 10 billion of non-neuronal cells. Out of these neurons, 16 billion (19%) are situated in the cerebral cortex, and 69 billion (80%) are in the cerebellum.