Human brain is highly evolved organ. It is the main controlling centre of nervous system. It is the part of the central nervous system. It is very well protected inside the cranium or cranial cavity.
The brain is enclosed by meninges which are protective coverings. There are hollow ventricles inside the brain which are filled up with cerebrospinal fluid. This fluid is protective and nourishing in function. The average weight of adult human brain is about 1300 — 1460 grams and there are approximately 100 billion neurons in the brain.
There are three main parts of the brain, viz. Cerebrum, cerebellum and medulla oblongata.
