Breathing

Nostril, windpipe, ribs, bronchi, diaphragm, lung.

Breathing is the process of taking in and expelling air. We need air because it contains oxygen. Oxygen enables our body to release the energy contained in our FOOD and keep us moving. When you sit still, you breathe in and out about twenty times every minute. When you run about, you need more energy than when you sit still, and so you need more oxygen. You breathe more quickly when you are running - perhaps as much as fifty times every minute.

Air is drawn in through the nose or the mouth.

Next, it passes into the windpipe. The windpipe divides into two passages, called bronchi. One of these goes to each lung. Our lungs are like two large balloons in the chest. When we breathe in, the MUSCLES between our ribs lift the rib cage and the sheet of muscle at the bottom of the ribs, called the diaphragm, pushes downwards. When this happens there is more space inside the ribs and the lungs can swell up as air is taken in.

Inside the lung the bronchi divide again and again forming a network of small air passages inside the lungs. Each one of these air passages ends in a tiny air sac called an alveolus. BLOOD collects oxygen from the alveoli and carries it round the body to all CELLS. When the cells use the oxygen, they produce another gas called carbon dioxide. Blood carried this gas back to the lungs and we breathe it out.

We do not have to think about breathing because we do it automatically. The BRAIN sends signals to the diaphragm and rib cage muscles, telling them how often to relax and tighten and so make us breathe in and out.

Nervous system

Brain, spinal cord, cerebellum, nerves.

The nervous system gather information about what is going on inside and outside our body using the SENSES and nerves. The BRAIN and spinal cord receive this information. They then send messages back which can make MUSCLES or CLANDS work. In this way we respond to situations around us. Sometimes we respond quickly and without thinking. If we touch something hot, we soon take our hand away. Often we choose what to do. When we cross a street we look, listen and thinks before we decide that it is safe to step forward.

Brain

The brain controls almost all the things that we do. Messages from all over the body pass to and from the brain along the spinal cord. Each part of the brain controls a different activity. Parts of the outer layer receive messages from the SENSES. Another area of the brain governs speech. The brain stores some information as memory. We learn from this memory and use its information to make decisions.

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