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Cells and Systems 6-8 / Week 06 / Wednesday
3/6
Week 06 · Systems Work Together

Wednesday

Windowsill Lab: Breaths and beats
// Lungs, heart and muscles share one job
⏱ about 20 min

Wednesday: Windowsill Lab: Breaths and Beats

Rocket has the timer in one hand and his other hand on his belly. "Resting breaths," he says. "I am ready."

"You have been sitting for two minutes," Raven says. "The rule is ten."

Rocket groans and sits back down. Nova hovers over the seed jars and measures a seedling while they wait.

At ten minutes Raven nods. Rocket counts quietly, lips moving, as the timer runs one full minute.

"Fourteen breaths," he says. "Now the run?"

"Predict first," Raven says. "What do you notice happened to your pulse last week after the jumps?"

"It went up. So breaths will go up too," Rocket says. "Both at once. That is my prediction."

Your mission

Today you count two things at rest and again after a short run: breaths per minute and heartbeats per minute.

Counting both lets you see whether the two systems change together. That is the evidence this week's standard asks for.

These are science readings for your own Log. They are not a health check, and nobody's numbers are compared.

  • A kitchen timer or phone timer that shows seconds
  • A chair, and a flat safe place for a short run or one minute of jogging in place
  • Shoes on, water nearby
  • Your Windowsill Log and a pencil
Safety first
Run on flat ground with shoes on, only as hard and as long as you are used to. One minute is enough.
Anyone who feels dizzy sits down right away and drinks water.
Count your pulse with two fingers on the wrist, never on the neck.
This is a science reading, not a health check. Your numbers stay in your own Log.
  1. Sit still for ten minutes. Then rest one hand on your belly.
  2. Start the timer. Count breaths for one full minute. One in and one out is one breath. Record it.
  3. Find your wrist pulse. Count beats for 30 seconds, multiply by 2, and record it.
  4. Stand up and jog in place or run a short distance for one minute at a pace you are used to.
  5. Sit down at once. Count breaths for one minute and record the number.
  6. Right away, count the pulse for 30 seconds, multiply by 2, and record it.
  7. Rest five minutes. Count breaths and pulse once more and record both.
ReadingBreaths per minuteBeats per minute
At rest, after 10 minutes sitting
Right after a one-minute run
After 5 more minutes of rest
PREDICT BEFORE YOU RUN
  • Read the question.
  • Tap your answer.
After the run, what do you predict happens to your breaths per minute?
After the run, what do you predict happens to your pulse?
One in and one out counts as how many breaths?

Reading your result

When you are not exerting yourself, people breathe approximately 15 times per minute on average, says the OpenStax text.

Running muscles need more oxygen and make more carbon dioxide. Both the lungs and the heart answer that demand.

So your breaths and your beats most likely rose together. One system brought in more oxygen, the other delivered it faster.

The two numbers do not rise by the same amount. Breathing and heartbeat are different systems with different speeds.

Your third reading shows both systems settling. The demand dropped, so both slowed down on their own.

What the lab showsTrue or false?
Breaths and beats were both counted at rest and after the run.?
A one-minute run should make breathing slower.?
Running muscles need more oxygen than resting muscles.?
Breathing and heartbeat always rise by exactly the same number.?
WHY THIS EXERCISETwo numbers rising together is the evidence that two systems interact.
You count 11 beats in 10 seconds. Multiply to find beats per minute. Type a number.
WHY THIS EXERCISEA short count scaled to one minute is the method the encyclopedia describes for an exercise pulse.
Draw two bar graphs side by side, one for breaths and one for beats, with your three readings in each.

Careful counting. Tomorrow you will read real breathing-rate tables and compare them with your Log.

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