central nervous system  

The nervous system can be divided into several connected systems that function together.Let's start with a simple division:The nervous system is divided into the central nervous system and peripheral nervous system. Let's break the central nervous system and the peripheral nervous system into more parts.
Central Nervous System:
The central nervous system is divided into two parts:the brain and the spinal cord.The average adult human brain weighs 1.3 to 1.4 kg(approximately 3pounds).The brain contains about 100 billion nerve cells (neurons)and trillons of "support cells"called glia.The spinal cord is about 43 cm long in adult women and 45 cm long in adult men and weighs about 35-40grams.The vertebral column,the collection of bones (back bone)that houses the spinal cord is about 70 cm long.Therefore, the spinal cord is much shorter than the vertebral column.