1. The Nervous System

2. What is the Nervous System?  The nervous system is the highway along which your brain sends and receives information about what is happening in the body and around it. This highway is made up of billions of nerve cells, or neurons (say new-rons) which join together to make nerves.  A nerve is a fiber that sends impulses through the body.

3.  These fibers are covered by fatty substance called myelin (my-e-lin). Myelin helps the messages go fast through the neurons.  Nerve cells work by a mixture of chemical and electrical action.  The two main parts of the nervous system are the central nervous system and the peripheral (per-if-er-al) nervous system.

5. Nerve cells – What is a neuron?  A neuron is a nerve cell. The brain is made up of approximately 100 billion neurons.  Neurons are similar to other cells in the body in some ways such as:  Neurons are surrounded by a membrane.  Neurons have a nucleus that contains genes.  Neurons contain cytoplasm, mitochondria and other "organelles".

6.  However, neurons differ from other cells in the body in some ways such as:  Neurons have specialized projections called dendrites and axons. Dendrites bring information to the cell body and axons take information away from the cell body.  Neurons communicate with each other through an electrochemical process.  Neurons form specialized connections called " synapses " and produce special chemicals called "neurotransmitters" that are released at the synapse.  There are approximately 1 quadrillion synapses in the human brain.

8. How nerve cells work  At the end of each nerve cell there is a synaptic terminal (sin-ap-tik term-in-ul). This is full of extremely tiny sacs which hold neurotransmitter chemicals (new-ro-trans- mitta- kem-ik-als).  These chemicals transmit nerve impulses from one nerve to another or from nerves to muscle cells.  An electrical nerve impulse travels along the neuron to these sacs which then release the neurotransmitter chemicals.

9.  The chemicals move along to the next neuron sparking an electrical charge which moves the nerve impulse forward.  This happens several times until the message gets where it's going.  It's a bit like you running around the house switching lights on. Pressing the switch causes electricity to flow through to the light bulb.

13. Parts of the Nervous System Central Nervous System Peripheral Nervous System

14. THE CENTRAL NERVOUS SYSTEM  The brain and the spinal cord make up the central nervous system.  Your spinal cord is a long bundle of neurons that goes down your back.  The brain lies protected inside the skull and from there controls all the body functions by sending and receiving messages through nerves.

15. The brain  The brain is the control center for your body and it sits in your skull at the top of your spinal cord.  The brain has three main parts.  The cerebellum (say se-re-bell-um).  The cerebrum (say se-re-brum), which has two parts, the left and right cerebral hemispheres, (say se-re-brell hem-iss-fears).  The brain stem, that controls a lot of the 'automatic' actions of your body such as breathing and heart beat, and links the brain to the spinal cord and the rest of the body.  Your brain is wrapped in 3 layers of tissue and floats in a special shock-proof fluid to stop it from getting bumped on the inside of your skull as your body moves around.

17. THE PERIPHERAL NERVOUS SYSTEM  The peripheral nervous system carries messages to and from the central nervous system. It sends information to the brain and carries out orders from the brain.  Messages travel through the cranial nerves, those which branch out from the brain and go to many places in the head such as the ears, eyes and face.  Messages can also travel through the spinal nerves which branch out from the spinal cord.

18. Nerves  Nerves are sort of like wires that carry communication signals or impulses around the body. Inside each nerve is a bundle of nerve fibers. Some nerves are really long, like the ones that go all the way from your feet to your spinal cord. Nerve cells are called neurons.  There are two main types of nerves: motor nerves and sensory nerves. Motor nerves  - Motor nerves allow the brain to control our muscles. The brain sends signals over the motor nerves to tell our muscles to expand or contract so we can move. Sensory nerves  - The second type of nerves are called sensory nerves. These nerves carry signals to the brain to tell it about what is going on in the outside world. They come from our skin (touch), nose (smell), eyes (sight), tongue (taste), nose (smell), and ears (hear).

19. Parts to the peripheral nervous system The somatic ( say so-mat-ik) system:  sends sensory information to the central nervous system through peripheral nerve fibers. Sensory means that it sends the information coming from all your senses, touch, vision, hearing, taste, smell and position.  sends messages to motor nerve fibers to get the muscles to move the body.

20. The autonomic ( say or-tow-nom-ik) system  is responsible for making sure that all the automatic things that your body needs to do to keep you going, like breathing, digesting etc. continue working smoothly without your having to think about them. (How hard would it be to have to keep thinking, "Breathe in, breathe out," or "Start digesting the food stomach!")

21. Helping the Nervous System  You can help your nervous system work well and be healthy by being active, having a healthy diet and keeping yourself busy and happy.  Exercise releases a chemical, called serotonin, in the brain which makes you feel good, relaxes muscles and gets rid of stress.  Good food gives your body the vitamins and minerals needed to build healthy nerves and tissue.  Keeping busy and happy helps you to deal with life when things go wrong.