G5 The Organs of the Body (On Grade)_01
Today is the big day. This is your first track meet you will be competing in. You have been practicing for many months. You will be competing in two events. The first will be the hurdles. You’ll have to leap as high as you can to jump over the hurdles without touching them. Then your body will need to rest to recover from the muscle strain. Later in the morning you will compete in the pole vault. The pole vault uses similar muscles as the hurdles. You’ll have to jump as high as you can and push yourself up into the air with the help of a long pole. Today your body must be at its best. To get ready you have trained hard for months. You have also been eating healthy and getting plenty of rest. To win an event like this all the organ systems in your body must be at their best.
Cardiovascular System
For the last six months you have been running after school. Some days you go for longer runs. Other days you run shorter distances and work only on your speed. When you first started working out, it was really hard to catch your breath. Your coach said you need to work on your “cardio.” Cardio is slang for the type of exercise that keeps your heart rate high.
The heart is the driving force of the Cardiovascular system. Your heart is like a pump. It pumps blood through your body. When you are exercising, your heart beats faster to pump more blood.
Imagine a city with a system of roads. There are smaller alleyways behind houses and buildings. Those small, narrow alleys connect to neighborhood streets which are bigger and wider to allow more cars to pass through. Those neighborhood streets then connect to main roads which might allow a car to travel from town to town. Those main roads then connect to major interstates, which allow cars to travel much longer distances between states. This is much like how the veins in your cardiovascular system work. Smaller capillaries are like alleyways, moving blood through your fingers and toes. Those capillaries connect to larger veins, which then intersect arteries. Arteries are the main highways that pump blood through your heart and lungs. That blood picks up oxygen in the arteries and then pushes back out to veins and capillaries, supplying your muscles and organs with the oxygen they need.