The elevated ridges of tissue on the surface of the cerebral hemispheres are known as the gyri.
The average human brain weighs about 1,400 grams (3 lb). The brain looks a little like a large pinkish-gray walnut. The brain can be divided down the middle lengthwise into two halves called the cerebral hemispheres.
Each cerebral hemisphere is divided into four lobes by sulci and gyri. The sulci (or fissures) are the grooves and the gyri are the "bumps" that can be seen on the surface of the brain. The folding created by the sulci and gyri increases the amount of cerebral cortex that can fit in the skull.
The total surface area of the cerebral cortex is about 324 square inches or about the size of a full page of newspaper. Each person has a unique pattern of gyri and sulci.
Tip! The human brain is the command center for the human nervous system. It receives input from the sensory organs and sends output to the muscles. The human brain has the same basic structure as other mammal brains, but is larger in relation to body size than any other brains. Get facts, functions and anatomy of the human brain at Livescience.com.