We discussed the spinal cord above (under “Brain and Nervous System Basics”) and explained that it extends from the brain and has the same layers (meninges) and CSF surrounding it (see Figure 4). The spinal cord makes up two thirds of the CNS and is a pathway for nerve impulses. Sensory information (such as touch, temperature, pressure, and pain) is carried to the brain. Commands that relate to movement (motor function) and reflexes travel from the brain to all parts of the body.
As you read this Web site, you do many things simultaneously. Your eyes are moving from left to right; you are holding the computer mouse and keyboard. You may be shifting in your chair. You may be aware of others in the room. You could also be listening to music and drinking a cup of tea or coffee, feeling the warmth of the cup in your hand. At the same time, you are thinking about what you are reading, filing away a few things in your mind for later consideration, maybe making a mental note to talk to your child’s doctor about something.
Like all living tissue, the brain and spinal cord are made up of cells, which in turn have characteristics and names unique to their function. The cells unique to the central nervous system are neurons and neuroglia.
Together, the brain and spinal cord make up the central nervous system, also referred to as the CNS. The network of nerves that connects the CNS to the arms, legs, eyes, ears, and other organs is called the peripheral nervous system (PNS). We are usually aware of our legs and arms moving and can generally control them. But other activities—such as blood circulation, breathing, digestion, and the work of hormones in our body—are carried out without our thinking much about them.