Human Nervous System - Central Nervous System (CNS)

The central nervous system (CNS) includes the brain and spinal cord. The brain, the main control centre of the body, is located within the protective cranial cavity. The spinal cord is safeguarded by the vertebral column. Surrounding the CNS are protective layers called meninges, and between these layers is a fluid called cerebrospinal fluid. This fluid fills the brain’s ventricles, the spinal cord's central canal, and the spaces around the meninges. It provides nutrients to the CNS and acts as a cushion to protect it from shocks.

Structure of Brain

Brain and spinal cord

• The brain of an adult human weighs about 1300–1400 grams and consists of approximately 100 billion neurons.
• The left side of our brain controls the right side of our body, and the right side of our brain controls the left side of the body.
• The left side of the brain controls speech, conversation, writing, logical thinking, etc., whereas the right side controls artistic abilities.

Left and right sides of brain

• The CNS consists of two main parts — the brain, which is enclosed within the cranium of the skull, and the spinal cord, which occupies the vertebral canal of the vertebral column.
• The brain and spinal cord are surrounded and protected by three layers of membranes collectively called meninges.
• The outermost layer, Dura mater, is a tough, non-vascular, fibrous membrane attached to the inner side of the cranium.
• The middle layer, Arachnoid mater, is made of connective tissue with a web-like appearance and is separated from the dura mater by the subdural space filled with serous fluid.
• The innermost layer, Pia mater, is a delicate and highly vascular membrane that remains in close contact with the CNS, supplying it with blood.