Reflex arc - playground model

Thursday 14 September 2017

Walking along a neurone and passing chemicals (sweets) to the next neurone could be a great way to illustrate the reflex arc with IB students. 

I recently tried this out at the end of term and my students remembered the event and some of the details enthusiastically in my first lesson this autumn.  While this is not scientific proof that the activity improves learning, I'm happy with a bit of anecdotal evidence and some enthusiastic memories from my class.

It's possible to do giant walk-through activities with many Biological mechanisms.
I first tried the concept to explain kidney nephrons with great success, then with the double circulation, the journey of a sandwich in the digestive system, and now the reflex arc.

Other potential topics might include, transport accross membranes, osmosis, transpiration, gas exchange in the alveoli and perhaps even blood clotting.

.  There is very little equipment required:

  • A few cones from the PE department
  • Several soft balls, or better still packets of sugary sweets - the kind that fizz in your mouth and react.
  • A set of giant chalks
  • Some nice weather.


It's important that students understand something about what they are doing, so a little theoretical preparation is essential and it's nice if the students have a basic understanding of the diagram which they have to draw.  I introduce a diagram of the subject in class then divide the diagram into several parts and give responsibility for each part to a small group of students. Their first task is to recreate the diagram on the tarmac.

Next step is to assign a specific role to each student.  For this reflex arc the following roles might be a good start:

  • Stimulus
  • Receptor cell
  • Sensory neurone impulse
  • Motor neurone impulse
  • Effector cell (muscle or gland)
  • Response

To help illustrate the diffusion of neurotransmitter we used a packet of 'crack-up' sweets - each student was given one packet.

  1. To start the reflex a ball was passed to the receptor cell from the stimulus.
  2. The receptor cell passed the sweet packet to the sensory neurone impulse.
  3. The impulse ran along the sensory neurone to it's end,
  4. The sensory impulse then opened the sweets and fed some to the relay neurone.
  5. The relay neurone impulse took the sweet packet and ran to the end of the relay neurone.
  6. Then the relay impulse fed sweets to the motor neurone impulse who ran to the end of the motor neurone, gave the sweets to the effector, who threw a ball to the response.
  7. The ball represents movement different to the impulses in the reflex arc.

Once everyone was clear about their roles and students had changed places a bit to learn the different roles we spiced up the activity by timing each groups fastest reaction time.

It's great fun, although slightly crazy, and a good way to introduce the components of a reflex arc in Neurones & synapses - planning 6.5.


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