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What Really Tells You to Breathe

8th grade nonfiction passage about how the body controls breathing: 258 words, six questions, an answer key and vocabulary.

8th grade nonfiction how the body controls breathing 258 words

What Really Tells You to Breathe

Most people assume that the urge to breathe means the body is running out of oxygen. The truth is a little different. The main trigger for breathing is carbon dioxide, a waste gas that your cells produce as they use oxygen to release energy from food.

Carbon dioxide travels in the blood to the lungs, where it is breathed out. If you breathe more slowly than your cells require, carbon dioxide builds up and makes the blood slightly more acidic. Special sensors in the brainstem and in large blood vessels notice this change. They send a message to the muscles that control breathing, mainly the diaphragm, a dome-shaped sheet beneath the lungs. The diaphragm tightens and flattens, the chest expands, and air rushes in. All of this happens without any thought, which is why you keep breathing while you sleep.

You can take some control, since you can pause for a moment or take a deep breath on purpose. But the automatic system always wins in the end. As carbon dioxide rises, the urge to breathe grows stronger and more uncomfortable until the body makes you inhale.

The same system explains why exercise makes you pant. Working muscles make more carbon dioxide, so the brain raises both the speed and the depth of your breathing to clear it away. When you rest, the carbon dioxide level falls and your breathing slows again. Thanks to these chemical sensors, a job that is vital to life can run safely on autopilot while your mind is busy with other things.

Questions

  1. What is the main trigger for breathing? in the text

  2. Where are the sensors that notice the change in the blood? in the text

  3. Which muscle does most of the work of breathing? in the text

  4. Why do you keep breathing while you are asleep? think about it

  5. Why does exercise make you pant? think about it

  6. What happens to the urge to breathe as carbon dioxide rises? in the text

Words to know

carbon dioxide
a waste gas that cells make and the lungs breathe out
diaphragm
the dome-shaped muscle under the lungs that pulls air in
brainstem
the part of the brain that joins it to the spinal cord
automatic
happening by itself without any thinking
acidic
having more acid, which changes the chemistry of a liquid
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One passage, three levels

The same topic and facts written three ways, so a mixed class can read and talk about one text. Each group’s sheet shows only a shape; the key says which is which.

● Easier · 221 words · Flesch-Kincaid grade 3

Many people think the urge to breathe means the body is out of oxygen. That is not quite right. The main trigger is carbon dioxide. This is a waste gas. Your cells make it when they use oxygen to get energy from food.

Carbon dioxide goes in the blood to the lungs. There, you breathe it out. If you breathe too slowly, carbon dioxide builds up. It makes the blood a little more acidic. Sensors in the brainstem and in big blood vessels notice this. They send a message to the muscles that run your breathing. The main one is the diaphragm. It is a dome-shaped sheet under the lungs. The diaphragm tightens and flattens. The chest gets bigger. Air rushes in. You do not have to think about it. That is why you keep breathing in your sleep.

You can take some control. You can stop for a moment or take a deep breath. But the automatic system wins in the end. As carbon dioxide goes up, the urge to breathe gets stronger. It gets uncomfortable. At last the body makes you breathe in.

The same system explains why you pant when you exercise. Working muscles make more carbon dioxide. So the brain makes you breathe faster and deeper. When you rest, the level drops and you slow down.

▲ This passage · 258 words · Flesch-Kincaid grade 7.4

Most people assume that the urge to breathe means the body is running out of oxygen. The truth is a little different. The main trigger for breathing is carbon dioxide, a waste gas that your cells produce as they use oxygen to release energy from food.

Carbon dioxide travels in the blood to the lungs, where it is breathed out. If you breathe more slowly than your cells require, carbon dioxide builds up and makes the blood slightly more acidic. Special sensors in the brainstem and in large blood vessels notice this change. They send a message to the muscles that control breathing, mainly the diaphragm, a dome-shaped sheet beneath the lungs. The diaphragm tightens and flattens, the chest expands, and air rushes in. All of this happens without any thought, which is why you keep breathing while you sleep.

You can take some control, since you can pause for a moment or take a deep breath on purpose. But the automatic system always wins in the end. As carbon dioxide rises, the urge to breathe grows stronger and more uncomfortable until the body makes you inhale.

The same system explains why exercise makes you pant. Working muscles make more carbon dioxide, so the brain raises both the speed and the depth of your breathing to clear it away. When you rest, the carbon dioxide level falls and your breathing slows again. Thanks to these chemical sensors, a job that is vital to life can run safely on autopilot while your mind is busy with other things.

■ Harder · 269 words · Flesch-Kincaid grade 9.7

Most people presume that the urge to take a breath signals that the body is running short of oxygen. The reality is somewhat different. The principal trigger for breathing is carbon dioxide, a waste gas that your cells generate as they use oxygen to release energy from the food you eat.

Carbon dioxide is carried by the blood to the lungs, where it is exhaled. Should you breathe more slowly than your cells require, carbon dioxide accumulates and renders the blood slightly more acidic. Specialized sensors in the brainstem and in large blood vessels detect this change and transmit a message to the muscles that control breathing, chiefly the diaphragm, a dome-shaped sheet lying beneath the lungs. The diaphragm tightens and flattens, the chest expands, and air rushes in. Because all of this occurs without any conscious thought, you continue to breathe while you sleep.

You can exert a degree of control, since you may pause briefly or draw a deep breath deliberately. Nevertheless, the automatic system always prevails in the end. As the level of carbon dioxide climbs, the urge to breathe grows steadily stronger and more uncomfortable, until the body compels you to inhale.

The same system explains why exercise makes you pant. Working muscles produce additional carbon dioxide, so the brain increases both the rate and the depth of your breathing in order to clear it away. Once you rest, the carbon dioxide level falls and your breathing slows again. Thanks to these chemical sensors, a task that is essential to life can run safely on autopilot while your mind is occupied with other matters.

Download as one PDF

How to use it

  1. Press Read it big (or B) to put the text on the projector, or Full screen (F) to fill the whole screen.
  2. Ask the questions one at a time and use Show answer when the class has decided. A shows or hides every answer.
  3. Print student copy for the class, or Print with answers for yourself.

Ideas for class

  • Before reading, put carbon dioxide, diaphragm, brainstem, automatic and acidic on the board with their meanings from the Words to know section and have students predict what the text will be about.
  • Read it aloud once while students follow along, then have them reread it alone or with a partner. At a calm 100 words a minute it takes about 3 minutes to read aloud.
  • Use the Read it big button (or B) to put the text on the projector, and Show answer on one question at a time so the class commits to an answer first.
  • Question 4 asks the reader to infer. Ask students to point to the words in the passage that led them to their answer.
  • Ask students to write one question the passage did not answer, then look for the answer in a book or on a classroom screen.
  • Print the student copy for independent work and keep the answer-key copy for yourself.

Related

Questions

What reading level is "What Really Tells You to Breathe"?

It was written for 8th grade. It has 258 words and works out to a Flesch-Kincaid grade level of about 7.4. That is a formula's estimate from sentence length and syllables, and it is not a Lexile or a guided reading level, so check it against your students.

What do the questions ask?

There are six. 4 ask for something the text says directly and 2 ask the reader to work something out from clues. Each has an answer in the key, and the answers are written as a teacher would accept them, not as the only possible wording.

How long does it take to read?

About 3 minutes read aloud at 100 words a minute. For a one-minute fluency check, paste it into the fluency timer and use the word count.

Can I print it?

Yes. Print student copy gives the passage, the questions with lines to write on, and the word meanings. Print with answers gives the same page with the answers filled in. Both are made in your browser.

Is this passage from a published book?

No. It was written for Peabody Teach, so there is no book to buy and no login to read it.

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