Introduction: Model of Sensory Pathways - Elementary School Project

A drawing enhanced by moving LED lights was used to develop a model of the sensory pathways in the human body. In particular, the touch and pain were described using the foot as the particular example. The idea is that once either touch or pain is triggered, the LED strips light up showing the path of the signals along the three neurons that form each pathway. Important points such as where the neuron synapses and passes the signal to another one and when the signals cross the spinal cord, reach the medulla, the thalamus and the cortex are also highlighted by pauses. The final "sensing" is done by text/sound display on the "brain".

It was part of a Year 6 (England), Grade 5 (US) school project on human physiology so the level of explanations and drawings were kept to that level.

The student was inspired by the "Sensory Pathways MADE EASY!!" video by Dr Matt & Dr Mike. The final project is detailed in "Sensory Pathways, Year 6 (ENG)/Grade 5 (US) project" .


Supplies

  • x2 Micro:Bit V2 : v1 would work but touch sensing should be replaced.
  • x1 WS2812B LEDs, 1m, 60 LEDs/m: Any length is fine the drawing can be adjusted.
  • x5 minimum alligator clips.
  • Assorted jump wires (DuPont cables), alligator clips.
  • Corrugated cardboard of appropriate size to hold the drawing: Can be replaced by other stiff materials.
  • Prototyping breadboard: Can be replaced by alligator clips, soldering etc.
  • Translucent drawing, cover paper.
  • Wire cutters, soldering equipment, tweezers, scissors, pen knives.
  • Pressure sensitive putty ("blue tack") , skotch tape, double sided tape. Basically materials to hold paper, cardboard, Micro:Bit and wires in place.

Step 1: Lay Down LED Strips

We have decided to use 30 LEDs of 60 LEDS/m strips for left & right regions of the spinal cord. Most of these LED strips come with indicators on where to cut and we have used wire cutters to cut the strip to end up with two 30 LED strips. Look their length and decide on the size of the cardboard you would need to cut. We left about ~20 cm extra all around.

Then we prepared the ends of the strips for use with typical prototyping wires or alligator clips by stripping off the wires. For one strip, we had to solder three wires to the contacts. You should end up with three wires in the "up" direction for both strips. There are numerous ways this could be done.

On the cardboard, decide how far apart to lay the strips. Ours was about ~5 cm apart and approximately parallel. We have held them in place with pressure sensitive putty ("blue tack") on the cardboard, approximately at its center.

Step 2: Decide the Position of the Neurons

Both the touch and pain pathways use three neurons. You can see this in the photo. Touch (green) has a "long-short-short" neuron arrangement. Whereas, pain (red) has a "short-long-short" arrangement. You need to decide how many LEDs to use for each one. We have started with 20 LEDs for "long" and 5 LEDs for "short" neurons. You will be able to modulate this to match your drawing afterwards.

Carefully place some marks with a pencil at the edges of the paper to allow its placement over the strips. Then use the pencil to trace the position of the strips. Do not color or use something permanent since you do not want two parallel lines. Your goal is know where to draw the "touch" and "pain" pathways shown on the photo and detailed in the youtube video "Sensory Pathways MADE EASY!!" (by Dr Matt & Dr Mike). We held the paper in place with the putty while doing this.

Step 3: Prepare the Electronics

We have used two BBC Micro:Bit V2's for this purpose. One of them will power and control the LED strips, sense touch and pain. The other acts as the brain and receives a radio signal when the signal (travelling light along the strip) reaches the brain.

Version 2 (V2) is different from version 1 (V1) , for the purposes of this instructable, in that it has a touch sensitive logo and a speaker. We have used the touch sensitive logo to illustrate the "touch" pathway and the speaker in one of them to make happy/sad sounds. These are both options. "Pin press" can instead be used to replace touch with less dramatic results. The LED panel on Micro:Bit spells out "touched" and "pain" or can show happy/sad faces instead of (in addition to) the sounds. Furthermore, second Micro:Bit can be skipped.

The next step is wiring. It is advisable to first wire everything with alligator clips (see my daughter's handwritten notes alongside the TinkerCad drawing) to test things. Note that the potato battery does not exist. I simply could not figure out a way to put two wires hanging free as sensors. We have attached the alligator clip to a nail to simulate "stepping on a nail" for "pain" but you can also just touch the two ends together.

Later on, you can arrange the wiring as needed. We have used a prototyping breadboard with jump wires (DuPont cables) and crocodile clips but this can be done multiple ways. If the project should be taken to the school or displayed publicly, it is better to take some time to stabilize the wiring.

Once this is done. Import the attached files (also available on the links) into two Micro:Bit Make Code projects. "microbit-touchpainprogramfinal.hex" is the one that controls the strips where as the "microbit-reciever-paintouch.hex" is for the receiver. Screen shots are included to show the steps but it is better vieweded on the Make Code web-site as an imported project. The codes are edited to fit our drawing. As mentioned before, you will have to do the same to match yours.

If everything is fine, you can touch the logo and you will see green LED lights moving up, stopping 3 times and the receiver Micro:Bit responding to this. Similarly, if the alligator clips connected to the ground and to the Pin 2 are connected, red lights will move up. The video "Sensory Pathways, Year 6 (ENG)/Grade 5 (US) project" shows the proper functioning.

If the LEDs do not display properly, a potential culprit is poor connections or short-circuits. These cause random colors, many LEDs turning on simultaneously etc.

Step 4: Draw the Pathways & Labels

The amount of detail you need for the drawing is up to you. The goal is to replicate what is detailed in the youtube video "Sensory Pathways MADE EASY!!" (by Dr Matt & Dr Mike) with printed (or hand-written) labels. Our labels were done on MS Powerpoint by a 10 year old, printed and cut. She decided which ones needed labeling and what the text should say as shown in the pdf file.

It is important to match the key aspects as following:

  • Both pathways start at the same point on the "foot".
  • Touch starts with a "long" neuron that goes to the bottom of the medulla, synapses to another neuron ("short"). The second neuron crosses over to the contralateral side and goes up to the thalamus. There it synapses and another neuron ("short") relays the information to the cerebral cortex.
  • Pain starts with a "short" neuron which synapses to a "long" neuron. The second neuron crosses over to the contralateral side, goes up to the thalamus, synapses. The third "short" neuron" picks up and relays the information to the cerebral cortex.
  • We did not match the correct position on the cerebral cortex. If you are inclined to do so, refer to the "Cortical Homunculus".
  • The shapes of different objects, two cerebral hemispheres etc should roughly resemble the right ones.
  • Do not forget to use your marks from Step 2 otherwise the lights will not be in the right places.

Cut the paper according to the size you want.

Step 5: Assemble and Fine Tune

Carefully place the drawing over the strips which have been mounted on the cardboard. There may be some tweaking needed but your goal is to roughly match the neurons with LEDs. Run the codes again and compare your results to the video "Sensory Pathways, Year 6 (ENG)/Grade 5 (US) project" . You may need to add/remove some steps from the loops for different LEDs, adjust the strip/paper positions to match your drawing.

In our case, the final project was accompanied with a video of my daughter explaining her project so we have adjusted the timing of everything to match her speech.

Other variations are possible. For example, the pain pathway also senses temperature and the Micro:Bit has a temperature sensor. You can add code for that and use a hairdyer to initiate the pain pathway.