Brain DeCoded with CodeX - Mission 5, Objective 5: Athlete Reaction

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Overview

The brain does not fire every motor neuron it has for every movement. It recruits what the job needs. Holding your posture uses tiny motor neurons on small muscles that can run all day without tiring. Sprinting recruits large motor neurons on large muscles, which deliver far more force and fatigue much faster.

Students build athlete_reaction, a reaction test driven by the potentiometer. Turning the knob is the movement, the program times it, and the results are drawn on the screen as waves so students can compare runs. That wave display is where the data analysis standard lives, and it is also the hook for the math extension.

Only the potentiometer is needed this time. No servo, so setup is lighter than the last two objectives.

🎯 Project Goal: Students add code to a program that simulates motor neuron recruitment.

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Learning Targets

I can explain how motor neurons are recruited by the brain to control muscles.

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Key Concepts

Tiny motor neurons are recruited for tiny muscles that do not tire easily, like posture muscles.
Increased physical activity with larger muscles requires larger motor neurons. These larger muscles fatigue more quickly.

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Assessment Opportunities

Turn in the Activity Guide.
Complete the program athlete_reaction.

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Success Criteria

Complete the CodeTrek steps
Program runs correctly without errors
Activity Guide is completed

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Digital Resources

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Classroom Materials

▸CodeX device and USB cable, one per student
▸Laptop/computer with Chrome browser
▸Potentiometer and divider

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Extensions & Cross-Curricular

ExtensionFor students with programming experience, have them review the code for get_speed() and change the function so the test starts with the knob on the right and turns to the left. Record the times. Does it make a difference which way you turn?

ExtensionChange the program to simulate a motion other than running, and adjust the text to describe the new motion.

MathThis program uses waves to represent data, and waves show up all over math. Add a lesson on waves and graphing, or on calculating frequency.

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New Python Code

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display.draw_line(0, 229, 239, 229, RED)Draw a line between point (0, 229) and point (239, 229).

run_type, col = determine_type(velocity)The two values returned by the function are assigned to two variables in the order given.

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Standards

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Computer Science

9-12.DA.10

Physical Science

HS-PS4-5

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Preparing for the Lesson

Count out a potentiometer with its divider per student or pair. No servo this time, so setup is quicker than Objectives 2 and 4.
Run the program yourself first and take the reaction test a couple of times. Knowing what a normal set of times looks like helps you spot a student whose knob is wired backward.
Decide how students get the Activity Guide. You can print a copy for each student or assign it digitally. They record their times in it, so hand it out before they start.
Have the CodeX Peripherals Guide open or projected for wiring questions.
Decide whether you are taking the math extension. If waves and frequency are on your scope and sequence, the wave display in this program is a ready-made entry point.

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Teacher Notes

The program uses the potentiometer. Remind students to use the divider board with the potentiometer, and to check that the wires are connected correctly.
Students should follow the instructions on the Activity Guide and record their results.
Recruitment is a matching idea, not a strength idea. The brain calls up the size of motor neuron the job needs, which is why students can hold a pencil all day and cannot sprint all day.
Reaction times vary a lot between students, and that is fine. Keep the comparison on a student's own runs rather than turning it into a contest across the room.
Extensions and cross-curricular projects are included to enhance the concepts in the objective. You can use the extensions to extend students' learning.

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Lesson Outline

🗣️Warm-up / Hook

Start with two jobs that use very different amounts of muscle.

Have students hold a pencil out at arm's length, then ask: "Could you do this for an hour? Could you sprint for an hour?"
Ask: "Your brain uses the same muscles for both. So what is it changing?"

Teaching tip: The pencil is the whole concept in ten seconds. Small job, small motor neurons, no fatigue. Students feel the difference instead of reading about it.

🔌Setup

Lighter setup than the last two objectives.

Hand out the potentiometer with its divider.
Students connect the potentiometer through the divider board and check wire order before running anything.
Hand out or assign the Activity Guide, since students record their times as they test.

Teaching tip: Students who wired this in Objectives 2 and 4 should be quick here. Turn a few of them loose to help the rest and you will be running code in a few minutes.

💻Student Work Time

Students build athlete_reaction and run the test.

Students work through the CodeTrek steps, adding code to athlete_reaction.
They draw the display with display.draw_line() and unpack the two returned values from determine_type() into two variables at once.
Students take the reaction test several times and watch the waves change with their results.
Students record their times on the Activity Guide as they go.

Teaching tip: Have students run the test at least three or four times. One run is a fluke, several runs are data, and the pattern is what the wave display is there to show.

📊Read the Waves

Turn the display into the recruitment idea. This is where the data standard gets earned.

Have students describe what their wave looks like for a fast run versus a slow one.
Ask which size of motor neuron a real body would recruit for each, and why the fast one tires sooner.
Ask what the wave picture tells them that a single number would not.

Teaching tip: If you are running the math extension, stop here and name the parts of the wave. Students are already looking at frequency and amplitude, they just do not have the words yet.

✏️Wrap-up & Review

Close on recruitment.

Ask: "In one sentence, how does your brain decide which motor neurons to use?"
Ask for one example of a posture muscle job and one athletic job, and which neurons each recruits.
Collect the Activity Guides. Have students return the potentiometers.

Teaching tip: Objective 6 closes the mission with brain training and practice, so a good last question is whether practice changes recruitment. Leave it hanging.

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