The brain and spinal cord make up the body’s central nervous system.
The central nervous system receives messages from cells called nerves, which are spread throughout the body (the peripheral nervous system). The brain interprets information and relays messages back through the nerves to muscles and organs.
The brain is the most important organ in the body, because it controls all voluntary and involuntary processes, such as learning, sensing, imagining, remembering, breathing, blood circulation and heart rate, body temperature, digestion and continence (urinary and bowel control).
There are two main sections of the brain:
- The cerebrum (the largest part)
- The cerebellum.
The spinal cord extends from the base of the brain to the base of the spinal column. It consists of nerve cells and bundles of nerves that connect the brain with all parts of the body through the peripheral nervous system.
The brain and spinal cord are surrounded and protected by membranes called the meninges, the skull and the vertebrae bones. Inside the skull, the brain floats in fluid called cerebrospinal fluid.
The brain, spinal cord and nerves consist of billions of cells called neurons, which are cells that process and transmit information. There are three major types of neural cells:
- sensory neurons, which respond to light, sound and touch
- motor neurons, which cause muscle contractions
- interneurons, which connect neurons within the brain and spinal cord.
Glial cells are the other main type of cell in the nervous system.
There are several different types of glial cells, including astrocytes and oligodendrocytes. Glial cells are the glue of the nervous system because they surround and insulate the neurons and hold the neurons in place. The glial cells also supply nutrients and oxygen to neurons and eliminate dead neurons and germs.