Year 8 Science · Unit 1 · Lesson 3
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Learning Goals
Real-world context
Australian middle-distance runner Catriona McKiernan once said that during a 400 m sprint, it feels like every system in her body is working at maximum effort. During intense running, oxygen demand in the leg muscles increases dramatically. The body must take in more oxygen, pump it to the muscles faster, and clear away waste products such as carbon dioxide and lactic acid, all at the same time.
(a) Name three organ systems that are most active during a 400 m sprint. For each one, explain specifically what it is doing and why it must work harder than at rest.
(b) Explain why these organ systems must work together rather than independently. What would happen if the respiratory system worked hard but the circulatory system did not speed up?
Order the steps
Number the steps from 1 to 6 to show the correct sequence of how the circulatory and respiratory systems work together to deliver oxygen to a muscle cell. Step 1 = what happens first.
| Order | Step |
|---|---|
| Oxygen diffuses from the air sacs (alveoli) in the lungs into the bloodstream | |
| Blood carrying oxygen is pumped out of the heart through arteries to the body | |
| Oxygen is released from haemoglobin in red blood cells and diffuses into the muscle cell | |
| Air (containing oxygen) is breathed into the lungs via the trachea and bronchi | |
| The muscle cell uses oxygen in its mitochondria to release energy for contraction | |
| Blood travels through capillaries to reach the muscle tissue |
1. The digestive system breaks down food into nutrients that enter the blood. Explain how this makes the digestive system dependent on the circulatory system to complete its job.
2. A student says, "The nervous system is the most important organ system because it controls everything else." Do you agree? Explain your answer using the idea of interdependence between organ systems.
Wrap Up
In one sentence, what was the main idea of this lesson?